Polypeptides having alpha-glucosidase activity and polynucleotides encoding same

ABSTRACT

The present invention relates to isolated polypeptides having alpha-glucosidase activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods for producing and using the polypeptides.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of pending U.S. application Ser. No.11/176,864, filed Jul. 6, 2005, now U.S. Pat. No. 7,368,271, whichclaims priority from U.S. provisional application Ser. No. 60/586,103,filed Jul. 6, 2004, which applications are fully incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to isolated polypeptides havingalpha-glucosidase activity and isolated polynucleotides encoding thepolypeptides. The invention also relates to nucleic acid constructs,vectors, and host cells comprising the polynucleotides as well asmethods for producing and using the polypeptides.

2. Description of the Related Art

Several enzymes are involved in the degradation of starch. The enzymesinclude alpha-amylase, beta-amylase, amyloglucosidase, pullulanase,isoamylase, alpha-glucosidase, and cylcodextrin glycosyltransferase.

Alpha-glucosidases (EC 3.2.1.20) hydrolyze terminal, non-reducingalpha-1,4-linked glucose residues in various substrates, releasingglucose. They degrade disaccharides and oligosaccharides quickly whilepolysaccharides are attacked slowly if at all. Maltose, maltosederivatives, sucrose, aryl-alpha-glucosides, and alkyl-alpha-glucosidescan act as substrates.

Other filamentous fungi have been reported to produce alpha-glucosidasessuch as Aspergillus fumigatus (Rudick and Elbein, 1974, Archives ofBiochemistry and Biophysics 1611: 281-290), Aspergillus flavus(Olutiola, 1981, Mycologia 73: 1130), Aspergillus nidulans (Kato et al.,2002, Appl. Environ. Microbiol. 68: 1250-1256), Aspergillus niger(Rudick et al., 1979, Archives of Biochemistry and Biophysics 193: 509),Aspergillus oryzae (Leibowitz and Mechlinski, 1926, Hoppe-Seyler'sZeitschrift für Physiologische Chemie 154: 64), Mortierella alliacea(Tanaka et al., 2002, Biosci. Biotechnol. Biochem. 66: 2415-2423), Mucorjavanicus (Yamasaki et al., 1978, Berichte des Ohara Instituts fürLandwirtschaftliche Biologie 17: 123), Mucor rouxii (Flores-Carreon andRuiz-Herrera, 1972, Biochemica et Biophysica Acta 258: 496), Penicilliumpupurogenum Yamasaki et al., 1976, Agricultural and Biological Chemistry40: 669), and Penicillium oxalicum (Yamasaki et al., 1977, Agriculturaland Biological Chemistry 41: 1451).

Alpha-glucosidases can be used in combination with otherstarch-degrading enzymes, e.g., alpha-amylase, to achieve completehydrolysis of starch in industrial applications where conversion tofermentable sugars is desirable. Consequently, there is a need in theart for alternative alpha-glucosidases with improved properties such aspH optimum, temperature optimum, and thermostability.

It is an object of the present invention to provide polypeptides havingalpha-glucosidase activity and polynucleotides encoding thepolypeptides.

SUMMARY OF THE INVENTION

The present invention relates to isolated polypeptides havingalpha-glucosidase activity selected from the group consisting of:

(a) a polypeptide having an amino acid sequence which has at least 85%identity with amino acids 21 to 960 of SEQ ID NO: 2;

(b) a polypeptide which is encoded by a nucleotide sequence whichhybridizes under at least high stringency conditions with (i)nucleotides 61 to 2880 of SEQ ID NO: 1, (ii) the genomic DNA sequencecomprising nucleotides 61 to 2880 of SEQ ID NO: 1, or (iii) acomplementary strand of (i) or (ii); and

(c) a variant comprising a conservative substitution, deletion, and/orinsertion of one or more amino acids of amino acids 21 to 960 of SEQ IDNO: 2.

The present invention also relates to isolated polynucleotides encodingpolypeptides having alpha-glucosidase activity, selected from the groupconsisting of:

(a) a polynucleotide encoding a polypeptide having an amino acidsequence which has at least 85% identity with amino acids 21 to 960 ofSEQ ID NO: 2;

(b) a polynucleotide having at least 85% identity with nucleotides 61 to2880 of SEQ ID NO: 1; and

(c) a polynucleotide which hybridizes under at least high stringencyconditions with (i) nucleotides 61 to 2880 of SEQ ID NO: 1, (ii) thegenomic DNA sequence comprising nucleotides 61 to 2880 of SEQ ID NO: 1,or (iii) a complementary strand of (i) or (ii).

The present invention also relates to nucleic acid constructs,recombinant expression vectors, and recombinant host cells comprisingthe polynucleotides.

The present invention also relates to methods for producing suchpolypeptides having alpha-glucosidase activity comprising (a)cultivating a recombinant host cell comprising a nucleic acid constructcomprising a polynucleotide encoding the polypeptide under conditionsconducive for production of the polypeptide; and (b) recovering thepolypeptide.

The present invention also relates to methods of using the polypeptides.

The present invention further relates to nucleic acid constructscomprising a gene encoding a protein, wherein the gene is operablylinked to a nucleotide sequence encoding a signal peptide consisting ofnucleotides 1 to 60 of SEQ ID NO: 1, wherein the gene is foreign to thefirst and second nucleotide sequences.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B show the cDNA sequence and the deduced amino acidsequence of a Fusarium venenatum alpha-glucosidase (SEQ ID NOs: 1 and 2,respectively).

FIG. 2 shows a restriction map of pEJG61.

FIG. 3 shows a restriction map of pJLin163.

FIG. 4 shows the dependence of the purified Fusarum venenatumalpha-glucosidase on pH in 50 mM sodium acetate-50 mM potassiumphosphate at 37° C.

FIG. 5 shows the thermostability of the purified Fusarium venenatumalpha-glucosidase after incubation in 50 mM sodium acetate pH 5.0 for 5minutes at different temperatures.

DEFINITIONS

Alpha-glucosidase activity: The term “alpha-glucosidase activity” isdefined herein as an alpha-D-glucoside glucohydrolase activity (E.C.3.2.1.20) which catalyzes the exohydrolysis of terminal, non-reducing1,4-linked alpha-D-glucose residues with the release of alpha-D-glucose.Natural substrates of the enzyme activity include, for example, maltose,maltotriose, maltotetraose, maltopentaose, starch (soluble), amylose,amylopectin, isomaltose, Kojibiose, sucrose, nigerose, turanose,melizitose, and glycogen. For purposes of the present invention,alpha-glucosidase activity is determined with maltose as substrate in0.1 M sodium acetate buffer pH 4.3 at 25° C. One unit ofalpha-glucosidase activity is defined as 1.0 mmole of glucose producedper minute at 25° C., pH 4.3 from maltose as substrate in sodium acetatebuffer.

The polypeptides of the present invention have at least 20%, preferablyat least 40%, more preferably at least 50%, more preferably at least60%, more preferably at least 70%, more preferably at least 80%, evenmore preferably at least 90%, most preferably at least 95%, and evenmost preferably at least 100% of the alpha-glucosidase activity of thepolypeptide consisting of the amino acid sequence shown as amino acids21 to 960 of SEQ ID NO: 2.

Isolated polypeptide: The term “isolated polypeptide” as used hereinrefers to a polypeptide which is at least 20% pure, preferably at least40% pure, more preferably at least 60% pure, even more preferably atleast 80% pure, most preferably at least 90% pure, and even mostpreferably at least 95% pure, as determined by SDS-PAGE.

Substantially pure polypeptide: The term “substantially purepolypeptide” denotes herein a polypeptide preparation which contains atmost 10%, preferably at most 8%, more preferably at most 6%, morepreferably at most 5%, more preferably at most 4%, more preferably atmost 3%, even more preferably at most 2%, most preferably at most 1%,and even most preferably at most 0.5% by weight of other polypeptidematerial with which it is natively or recombinantly associated. It is,therefore, preferred that the substantially pure polypeptide is at least92% pure, preferably at least 94% pure, more preferably at least 95%pure, more preferably at least 96% pure, more preferably at least 96%pure, more preferably at least 97% pure, more preferably at least 98%pure, even more preferably at least 99%, most preferably at least 99.5%pure, and even most preferably 100% pure by weight of the totalpolypeptide material present in the preparation.

The polypeptides of the present invention are preferably in asubstantially pure form. In particular, it is preferred that thepolypeptides are in “essentially pure form”, i.e., that the polypeptidepreparation is essentially free of other polypeptide material with whichit is natively or recombinantly associated. This can be accomplished,for example, by preparing the polypeptide by means of well-knownrecombinant methods or by classical purification methods.

Herein, the term “substantially pure polypeptide” is synonymous with theterms “isolated polypeptide” and “polypeptide in isolated form.”

Identity: The relatedness between two amino acid sequences or betweentwo nucleotide sequences is described by the parameter “identity”.

For purposes of the present invention, the degree of identity betweentwo amino acid sequences is determined by the Clustal method (Higgins,1989, CABIOS 5: 151-153) using the LASERGENE™ MEGALIGN™ software(DNASTAR, Inc., Madison, Wis.) with an identity table and the followingmultiple alignment parameters: Gap penalty of 10 and gap length penaltyof 10. Pairwise alignment parameters are Ktuple=1, gap penalty=3,windows=5, and diagonals=5.

For purposes of the present invention, the degree of identity betweentwo nucleotide sequences is determined by the Wilbur-Lipman method(Wilbur and Lipman, 1983, Proceedings of the National Academy of ScienceUSA 80: 726-730) using the LASERGENE™ MEGALIGN™ software (DNASTAR, Inc.,Madison, Wis.) with an identity table and the following multiplealignment parameters: Gap penalty of 10 and gap length penalty of 10.Pairwise alignment parameters are Ktuple=3, gap penalty=3, andwindows=20.

Polypeptide Fragment: The term “polypeptide fragment” is defined hereinas a polypeptide having one or more amino acids deleted from the aminoand/or carboxyl terminus of SEQ ID NO: 2 or a homologous sequencethereof, wherein the fragment has alpha-glucosidase activity.Preferably, a fragment contains at least 790 amino acid residues, morepreferably at least 840 amino acid residues, and most preferably atleast 890 amino acid residues of SEQ ID NO: 2.

Allelic variant: The term “allelic variant” denotes herein any of two ormore alternative forms of a gene occupying the same chromosomal locus.Allelic variation arises naturally through mutation, and may result inpolymorphism within populations. Gene mutations can be silent (no changein the encoded polypeptide) or may encode polypeptides having alteredamino acid sequences. An allelic variant of a polypeptide is apolypeptide encoded by an allelic variant of a gene.

Substantially pure polynucleotide: The term “substantially purepolynucleotide” as used herein refers to a polynucleotide preparationfree of other extraneous or unwanted nucleotides and in a form suitablefor use within genetically engineered protein production systems. Thus,a substantially pure polynucleotide contains at most 10%, preferably atmost 8%, more preferably at most 6%, more preferably at most 5%, morepreferably at most 4%, more preferably at most 3%, even more preferablyat most 2%, most preferably at most 1%, and even most preferably at most0.5% by weight of other polynucleotide material with which it isnatively or recombinantly associated. A substantially purepolynucleotide may, however, include naturally occurring 5′ and 3′untranslated regions, such as promoters and terminators. It is preferredthat the substantially pure polynucleotide is at least 90% pure,preferably at least 92% pure, more preferably at least 94% pure, morepreferably at least 95% pure, more preferably at least 96% pure, morepreferably at least 97% pure, even more preferably at least 98% pure,most preferably at least 99%, and even most preferably at least 99.5%pure by weight. The polynucleotides of the present invention arepreferably in a substantially pure form. In particular, it is preferredthat the polynucleotides disclosed herein are in “essentially pureform”, i.e., that the polynucleotide preparation is essentially free ofother polynucleotide material with which it is natively or recombinantlyassociated. Herein, the term “substantially pure polynucleotide” issynonymous with the terms “isolated polynucleotide” and “polynucleotidein isolated form.” The polynucleotides may be of genomic, cDNA, RNA,semisynthetic, synthetic origin, or any combinations thereof.

Subsequence: The term “subsequence” is defined herein as a nucleotidesequence having one or more nucleotides deleted from the 5′ and/or 3′end of SEQ ID NO: 1 or a homologous sequence thereof, wherein thesubsequence encodes a polypeptide fragment having alpha-glucosidaseactivity. Preferably, a subsequence contains at least 2370 nucleotides,more preferably at least 2520 nucleotides, and most preferably at least2670 nucleotides.

cDNA: The term “cDNA” is defined herein as a DNA molecule which can beprepared by reverse transcription from a mature, spliced, mRNA moleculeobtained from a eukaryotic cell. cDNA lacks intron sequences that areusually present in the corresponding genomic DNA. The initial, primaryRNA transcript is a precursor to mRNA which is processed through aseries of steps before appearing as mature spliced mRNA. These stepsinclude the removal of intron sequences by a process called splicing.cDNA derived from mRNA lacks, therefore, any intron sequences.

Nucleic acid construct: The term “nucleic acid construct” as used hereinrefers to a nucleic acid molecule, either single- or double-stranded,which is isolated from a naturally occurring gene or which is modifiedto contain segments of nucleic acids in a manner that would nototherwise exist in nature. The term nucleic acid construct is synonymouswith the term “expression cassette” when the nucleic acid constructcontains the control sequences required for expression of a codingsequence of the present invention.

Control sequence: The term “control sequences” is defined herein toinclude all components, which are necessary or advantageous for theexpression of a polynucleotide encoding a polypeptide of the presentinvention. Each control sequence may be native or foreign to thenucleotide sequence encoding the polypeptide or native or foreign toeach other. Such control sequences include, but are not limited to, aleader, polyadenylation sequence, propeptide sequence, promoter, signalpeptide sequence, and transcription terminator. At a minimum, thecontrol sequences include a promoter, and transcriptional andtranslational stop signals. The control sequences may be provided withlinkers for the purpose of introducing specific restriction sitesfacilitating ligation of the control sequences with the coding region ofthe nucleotide sequence encoding a polypeptide.

Operably linked: The term “operably linked” denotes herein aconfiguration in which a control sequence is placed at an appropriateposition relative to the coding sequence of the polynucleotide sequencesuch that the control sequence directs the expression of the codingsequence of a polypeptide.

Coding sequence: When used herein the term “coding sequence” means anucleotide sequence, which directly specifies the amino acid sequence ofits protein product. The boundaries of the coding sequence are generallydetermined by an open reading frame, which usually begins with the ATGstart codon or alternative start codons such as GTG and TTG. The codingsequence may a DNA, cDNA, or recombinant nucleotide sequence.

Expression: The term “expression” includes any step involved in theproduction of the polypeptide including, but not limited to,transcription, post-transcriptional modification, translation,post-translational modification, and secretion.

Expression vector: The term “expression vector” is defined herein as alinear or circular DNA molecule that comprises a polynucleotide encodinga polypeptide of the invention, and which is operably linked toadditional nucleotides that provide for its expression.

Host cell: The term “host cell”, as used herein, includes any cell typewhich is susceptible to transformation, transfection, transduction, andthe like with a nucleic acid construct comprising a polynucleotide ofthe present invention.

Modification: The term “modification” means herein any chemicalmodification of the polypeptide consisting of the amino acids 21 to 960of SEQ ID NO: 2 or a homologous sequence thereof, as well as geneticmanipulation of the DNA encoding that polypeptide. The modification canbe substitutions, deletions and/or insertions of one or more amino acidsas well as replacements of one or more amino acid side chains.

Artificial variant: When used herein, the term “artificial variant”means a polypeptide having alpha-glucosidase activity produced by anorganism expressing a modified nucleotide sequence of SEQ ID NO: 1. Themodified nucleotide sequence is obtained through human intervention bymodification of the nucleotide sequence disclosed in SEQ ID NO: 1.

DETAILED DESCRIPTION OF THE INVENTION Polypeptides HavingAlpha-Glucosidase Activity

In a first aspect, the present invention relates to isolatedpolypeptides having an amino acid sequence which has a degree ofidentity to amino acids 21 to 960 of SEQ ID NO: 2 (i.e., the maturepolypeptide) of at least 85%, preferably at least 90%, more preferablyat least 95%, and most preferably at least 97%, which havealpha-glucosidase activity (hereinafter “homologous polypeptides”). In apreferred aspect, the homologous polypeptides have an amino acidsequence which differs by ten amino acids, preferably by five aminoacids, more preferably by four amino acids, even more preferably bythree amino acids, most preferably by two amino acids, and even mostpreferably by one amino acid from amino acids 21 to 960 of SEQ ID NO: 2.

A polypeptide of the present invention preferably comprises the aminoacid sequence of SEQ ID NO: 2 or an allelic variant thereof; or afragment thereof that has alpha-glucosidase activity. In a preferredaspect, a polypeptide comprises the amino acid sequence of SEQ ID NO: 2.In another preferred aspect, a polypeptide comprises amino acids 21 to960 of SEQ ID NO: 2, or an allelic variant thereof; or a fragmentthereof that has alpha-glucosidase activity. In another preferredaspect, a polypeptide comprises amino acids 21 to 960 of SEQ ID NO: 2.In another preferred aspect, a polypeptide consists of the amino acidsequence of SEQ ID NO: 2 or an allelic variant thereof; or a fragmentthereof that has alpha-glucosidase activity. In another preferredaspect, a polypeptide consists of the amino acid sequence of SEQ ID NO:2. In another preferred aspect, a polypeptide consists of amino acids 21to 960 of SEQ ID NO: 2 or an allelic variant thereof; or a fragmentthereof that has alpha-glucosidase activity. In another preferredaspect, a polypeptide consists of amino acids 21 to 960 of SEQ ID NO: 2.

In a second aspect, the present invention relates to isolatedpolypeptides having alpha-glucosidase activity which are encoded bypolynucleotides which hybridize under very low stringency conditions,preferably low stringency conditions, more preferably medium stringencyconditions, more preferably medium-high stringency conditions, even morepreferably high stringency conditions, and most preferably very highstringency conditions with (i) nucleotides 61 to 2880 of SEQ ID NO: 1,(ii) the genomic DNA sequence comprising nucleotides 61 to 2880 of SEQID NO: 1, (iii) a subsequence of (i) or (ii), or (iv) a complementarystrand of (i), (ii), or (iii) (J. Sambrook, E. F. Fritsch, and T.Maniatus, 1989, Molecular Cloning, A Laboratory Manual, 2d edition, ColdSpring Harbor, N.Y.). A subsequence of SEQ ID NO: 1 contains at least100 contiguous nucleotides or preferably at least 200 continguousnucleotides. Moreover, the subsequence may encode a polypeptide fragmentwhich has alpha-glucosidase activity.

The nucleotide sequence of SEQ ID NO: 1 or a subsequence thereof, aswell as the amino acid sequence of SEQ ID NO: 2 or a fragment thereof,may be used to design a nucleic acid probe to identify and clone DNAencoding polypeptides having alpha-glucosidase activity from strains ofdifferent genera or species according to methods well known in the art.In particular, such probes can be used for hybridization with thegenomic DNA or cDNA of the genus or species of interest, followingstandard Southern blotting procedures, in order to identify and isolatethe corresponding gene therein. Such probes can be considerably shorterthan the entire sequence, but should be at least 14, preferably at least25, more preferably at least 35, and most preferably at least 70nucleotides in length. It is, however, preferred that the nucleic acidprobe is at least 100 nucleotides in length. For example, the nucleicacid probe may be at least 200 nucleotides, preferably at least 300nucleotides, more preferably at least 400 nucleotides, or mostpreferably at least 500 nucleotides in length. Even longer probes may beused, e.g., nucleic acid probes which are at least 600 nucleotides, atleast preferably at least 700 nucleotides, more preferably at least 800nucleotides, or most preferably at least 900 nucleotides in length. BothDNA and RNA probes can be used. The probes are typically labeled fordetecting the corresponding gene (for example, with ³²P, ³H, ³⁵S,biotin, or avidin). Such probes are encompassed by the presentinvention.

A genomic DNA or cDNA library prepared from such other organisms may,therefore, be screened for DNA which hybridizes with the probesdescribed above and which encodes a polypeptide having alpha-glucosidaseactivity. Genomic or other DNA from such other organisms may beseparated by agarose or polyacrylamide gel electrophoresis, or otherseparation techniques. DNA from the libraries or the separated DNA maybe transferred to and immobilized on nitrocellulose or other suitablecarrier material. In order to identify a clone or DNA which ishomologous with SEQ ID NO: 1 or a subsequence thereof, the carriermaterial is used in a Southern blot.

For purposes of the present invention, hybridization indicates that thenucleotide sequence hybridizes to a labeled nucleic acid probecorresponding to the nucleotide sequence shown in SEQ ID NO: 1, itscomplementary strand, or a subsequence thereof, under very low to veryhigh stringency conditions. Molecules to which the nucleic acid probehybridizes under these conditions can be detected using, for example,X-ray film.

In a preferred aspect, the nucleic acid probe is a polynucleotidesequence which encodes the polypeptide of SEQ ID NO: 2, or a subsequencethereof. In another preferred aspect, the nucleic acid probe is SEQ IDNO: 1. In another preferred aspect, the nucleic acid probe is the maturepolypeptide coding region of SEQ ID NO: 1. In another preferred aspect,the nucleic acid probe is the polynucleotide sequence contained inplasmid pFD11F2 which is contained in E. coli NRRL B-30753, wherein thepolynucleotide sequence thereof encodes a polypeptide havingalpha-glucosidase activity. In another preferred aspect, the nucleicacid probe is the mature polypeptide coding region contained in plasmidpFD11F2 which is contained in E. coli NRRL B30753.

For long probes of at least 100 nucleotides in length, very low to veryhigh stringency conditions are defined as prehybridization andhybridization at 42° C. in 5×SSPE, 0.3% SDS, 200 μg/ml sheared anddenatured salmon sperm DNA, and either 25% formamide for very low andlow stringencies, 35% formamide for medium and medium-high stringencies,or 50% formamide for high and very high stringencies, following standardSouthern blotting procedures for 12 to 24 hours optimally.

For long probes of at least 100 nucleotides in length, the carriermaterial is finally washed three times each for 15 minutes using 2×SSC,0.2% SDS preferably at least at 45° C. (very low stringency), morepreferably at least at 50° C. (low stringency), more preferably at leastat 55° C. (medium stringency), more preferably at least at 60° C.(medium-high stringency), even more preferably at least at 65° C. (highstringency), and most preferably at least at 70° C. (very highstringency).

For short probes which are about 15 nucleotides to about 70 nucleotidesin length, stringency conditions are defined as prehybridization,hybridization, and washing post-hybridization at about 5° C. to about10° C. below the calculated T_(m) using the calculation according toBolton and McCarthy (1962, Proceedings of the National Academy ofSciences USA 48:1390) in 0.9 M NaCl, 0.09 M Tris-HCl pH 7.6, 6 mM EDTA,0.5% NP-40, 1×Denhardt's solution, 1 mM sodium pyrophosphate, 1 mMsodium monobasic phosphate, 0.1 mM ATP, and 0.2 mg of yeast RNA per mlfollowing standard Southern blotting procedures for 12 to 24 hoursoptimally.

For short probes which are about 15 nucleotides to about 70 nucleotidesin length, the carrier material is washed once in 6×SCC plus 0.1% SDSfor 15 minutes and twice each for 15 minutes using 6×SSC at 5° C. to 10°C. below the calculated T_(m).

In a third aspect, the present invention relates to isolatedpolypeptides having alpha-glucosidase activity having the followingphysicochemical properties: a pH optimum in the range of about 4.5 toabout 6.0, preferably about 4.7 to about 5.7, more preferably about 4.8to about 5.5, most preferably about 5.0 to about 5.3, and even mostpreferably at pH 5.0 in 50 mM sodium acetate buffer/50 mM potassiumphosphate buffer at 37° C., and thermostability up to about 65° C.(approximately 77% residual activity) in 50 mM sodium acetate pH 5.0 for5 minutes.

In a fourth aspect, the present invention relates to artificial variantscomprising a conservative substitution, deletion, and/or insertion ofone or more amino acids of SEQ ID NO: 2 or the mature polypeptidethereof. Preferably, amino acid changes are of a minor nature, that isconservative amino acid substitutions or insertions that do notsignificantly affect the folding and/or activity of the protein; smalldeletions, typically of one to about 30 amino acids; small amino- orcarboxyl-terminal extensions, such as an amino-terminal methionineresidue; a small linker peptide of up to about 20-25 residues; or asmall extension that facilitates purification by changing net charge oranother function, such as a poly-histidine tract, an antigenic epitopeor a binding domain.

Examples of conservative substitutions are within the group of basicamino acids (arginine, lysine and histidine), acidic amino acids(glutamic acid and aspartic acid), polar amino acids (glutamine andasparagine), hydrophobic amino acids (leucine, isoleucine and valine),aromatic amino acids (phenylalanine, tryptophan and tyrosine), and smallamino acids (glycine, alanine, serine, threonine and methionine). Aminoacid substitutions which do not generally alter specific activity areknown in the art and are described, for example, by H. Neurath and R. L.Hill, 1979, In, The Proteins, Academic Press, New York. The mostcommonly occurring exchanges are Ala/Ser, Val/Ile, Asp/Glu, Thr/Ser,Ala/Gly, Ala/Thr, Ser/Asn, Ala/Val, Ser/Gly, Tyr/Phe, Ala/Pro, Lys/Arg,Asp/Asn, Leu/Ile, Leu/Val, Ala/Glu, and Asp/Gly.

In addition to the 20 standard amino acids, non-standard amino acids(such as 4-hydroxyproline, 6-N-methyl lysine, 2-aminoisobutyric acid,isovaline, and alpha-methyl serine) may be substituted for amino acidresidues of a wild-type polypeptide. A limited number ofnon-conservative amino acids, amino acids that are not encoded by thegenetic code, and unnatural amino acids may be substituted for aminoacid residues. “Unnatural amino acids” have been modified after proteinsynthesis, and/or have a chemical structure in their side chain(s)different from that of the standard amino acids. Unnatural amino acidscan be chemically synthesized, and preferably, are commerciallyavailable, and include pipecolic acid, thiazolidine carboxylic acid,dehydroproline, 3- and 4-methylproline, and 3,3-dimethylproline.

Alternatively, the amino acid changes are of such a nature that thephysico-chemical properties of the polypeptides are altered. Forexample, amino acid changes may improve the thermal stability of thepolypeptide, alter the substrate specificity, change the pH optimum, andthe like.

Essential amino acids in the parent polypeptide can be identifiedaccording to procedures known in the art, such as site-directedmutagenesis or alanine-scanning mutagenesis (Cunningham and Wells, 1989,Science 244: 1081-1085). In the latter technique, single alaninemutations are introduced at every residue in the molecule, and theresultant mutant molecules are tested for biological activity (i.e.,alpha-glucosidase activity) to identify amino acid residues that arecritical to the activity of the molecule. See also, Hilton et al., 1996,J. Biol. Chem. 271: 4699-4708. The active site of the enzyme or otherbiological interaction can also be determined by physical analysis ofstructure, as determined by such techniques as nuclear magneticresonance, crystallography, electron diffraction, or photoaffinitylabeling, in conjunction with mutation of putative contact site aminoacids. See, for example, de Vos et al., 1992, Science 255: 306-312;Smith et al., 1992, J. Mol. Biol. 224: 899-904; Wlodaver et al., 1992,FEBS Lett. 309: 59-64. The identities of essential amino acids can alsobe inferred from analysis of identities with polypeptides which arerelated to a polypeptide according to the invention.

Single or multiple amino acid substitutions can be made and tested usingknown methods of mutagenesis, recombination, and/or shuffling, followedby a relevant screening procedure, such as those disclosed byReidhaar-Olson and Sauer, 1988, Science 241: 53-57; Bowie and Sauer,1989, Proc. Natl. Acad. Sci. USA 86: 2152-2156; WO 95/17413; or WO95/22625. Other methods that can be used include error-prone PCR, phagedisplay (e.g., Lowman et al., 1991, Biochem. 30:10832-10837; U.S. Pat.No. 5,223,409; WO 92/06204), and region-directed mutagenesis (Derbyshireet al., 1986, Gene 46: 145; Ner et al., 1988, DNA 7:127).

Mutagenesis/shuffling methods can be combined with high-throughput,automated screening methods to detect activity of cloned, mutagenizedpolypeptides expressed by host cells. Mutagenized DNA molecules thatencode active polypeptides can be recovered from the host cells andrapidly sequenced using standard methods in the art. These methods allowthe rapid determination of the importance of individual amino acidresidues in a polypeptide of interest, and can be applied topolypeptides of unknown structure.

The total number of amino acid substitutions, deletions and/orinsertions of amino acids 21 to 960 of SEQ ID NO: 2 is 10, preferably 9,more preferably 8, more preferably 7, more preferably at most 6, morepreferably at most 5, more preferably 4, even more preferably 3, mostpreferably 2, and even most preferably 1.

Sources of Polypeptides Having Alpha-Glucosidase Activity

A polypeptide of the present invention may be obtained frommicroorganisms of any genus. For purposes of the present invention, theterm “obtained from” as used herein in connection with a given sourceshall mean that the polypeptide encoded by a nucleotide sequence isproduced by the source or by a cell in which the nucleotide sequencefrom the source has been inserted. In a preferred aspect, thepolypeptide obtained from a given source is secreted extracellularly.

A polypeptide of the present invention may be a bacterial polypeptide.For example, the polypeptide may be a gram positive bacterialpolypeptide such as a Bacillus polypeptide, e.g., a Bacillusalkalophilus, Bacillus amyloliquefaciens, Bacillus brevis, Bacilluscirculans, Bacillus coagulans, Bacillus lautus, Bacillus lentus,Bacillus licheniformis, Bacillus megaterium, Bacillusstearothermophilus, Bacillus subtilis, or Bacillus thuringiensispolypeptide; or a Streptomyces polypeptide, e.g., a Streptomyceslividans or Streptomyces murinus polypeptide; or a gram negativebacterial polypeptide, e.g., an E. coli or a Pseudomonas sp.polypeptide.

A polypeptide of the present invention may also be a fungal polypeptide,and more preferably a yeast polypeptide such as a Candida,Kluyveromyces, Pichia, Saccharomyces, Schizosaccharomyces, or Yarrowiapolypeptide; or more preferably a filamentous fungal polypeptide such asan Acremonium, Aspergillus, Aureobasidium, Cryptococcus, Filibasidium,Fusarium, Humicola, Magnaporthe, Mucor, Myceliophthora, Neocallimastix,Neurospora, Paecilomyces, Penicillium, Piromyces, Schizophyllum,Talaromyces, Thermoascus, Thielavia, Tolypocladium, or Trichodermapolypeptide.

In a preferred aspect, the polypeptide is a Saccharomycescarlsbergensis, Saccharomyces cerevisiae, Saccharomyces diastaticus,Saccharomyces douglasii, Saccharomyces kluyveri, Saccharomycesnorbensis, or Saccharomyces oviformis polypeptide havingalpha-glucosidase activity.

In another preferred aspect, the polypeptide is an Aspergillusaculeatus, Aspergillus awamori, Aspergillus fumigatus, Aspergillusfoetidus, Aspergillus japonicus, Aspergillus nidulans, Aspergillusniger, Aspergillus oryzae, Humicola insolens, Humicola lanuginosa, Mucormiehei, Myceliophthora thermophila, Neurospora crassa, Penicilliumpurpurogenum, Trichoderma harzianum, Trichoderma koningii, Trichodermalongibrachiatum, Trichoderma reesei, or Trichoderma viride polypeptidehaving alpha-glucosidase activity.

In another preferred aspect, the polypeptide is an Fusariumbactridioides, Fusarium cerealis, Fusarium crookwellense, Fusariumculmorum, Fusarium graminearum, Fusarium graminum, Fusariumheterosporum, Fusarium negundi, Fusarium oxysporum, Fusariumreticulatum, Fusarium roseum, Fusarium sambucinum, Fusarium sarcochroum,Fusarium sporotrichioides, Fusarium sulphureum, Fusarium torulosum,Fusarium trichothecioides, Fusarium venenatum polypeptide havingalpha-glucosidase activity.

In a more preferred aspect, the polypeptide is a Fusarium venenatumpolypeptide, and most preferably a Fusarium venenatum NRRL 30747polypeptide, e.g., the polypeptide of SEQ ID NO: 2 or amino acids 21 to960 of SEQ ID NO: 2.

It will be understood that for the aforementioned species, the inventionencompasses both the perfect and imperfect states, and other taxonomicequivalents, e.g., anamorphs, regardless of the species name by whichthey are known. Those skilled in the art will readily recognize theidentity of appropriate equivalents.

Strains of these species are readily accessible to the public in anumber of culture collections, such as the American Type CultureCollection (ATCC), Deutsche Sammiung von Mikroorganismen undZellkulturen GmbH (DSM), Centraalbureau Voor Schimmelcultures (CBS), andAgricultural Research Service Patent Culture Collection, NorthernRegional Research Center (NRRL).

Furthermore, such polypeptides may be identified and obtained from othersources including microorganisms isolated from nature (e.g., soil,composts, water, etc.) using the above-mentioned probes. Techniques forisolating microorganisms from natural habitats are well known in theart. The polynucleotide may then be obtained by similarly screening agenomic DNA or cDNA library of another microorganism. Once apolynucleotide sequence encoding a polypeptide has been detected withthe probe(s), the polynucleotide can be isolated or cloned by utilizingtechniques which are well known to those of ordinary skill in the art(see, e.g., Sambrook et al., 1989, supra).

Polypeptides of the present invention also include fused polypeptides orcleavable fusion polypeptides in which another polypeptide is fused atthe N-terminus or the C-terminus of the polypeptide or fragment thereof.A fused polypeptide is produced by fusing a nucleotide sequence (or aportion thereof) encoding another polypeptide to a nucleotide sequence(or a portion thereof) of the present invention. Techniques forproducing fusion polypeptides are known in the art, and include ligatingthe coding sequences encoding the polypeptides so that they are in frameand that expression of the fused polypeptide is under control of thesame promoter(s) and terminator.

Polynucleotides

The present invention also relates to isolated polynucleotides having anucleotide sequence which encode a polypeptide of the present invention.In a preferred aspect, the nucleotide sequence is set forth in SEQ IDNO: 1. In another more preferred aspect, the nucleotide sequence is thesequence contained in plasmid pFD11F2 which is contained in E. coli NRRLB30753. In another preferred aspect, the nucleotide sequence is themature polypeptide coding region of SEQ ID NO: 1. In another morepreferred aspect, the nucleotide sequence is the mature polypeptidecoding region contained in plasmid pFD11F2 which is contained in E. coliNRRL B-30753. The present invention also encompasses nucleotidesequences which encode a polypeptide having the amino acid sequence ofSEQ ID NO: 2 or the mature polypeptide thereof, which differ from SEQ IDNO: 1 by virtue of the degeneracy of the genetic code. The presentinvention also relates to subsequences of SEQ ID NO: 1 which encodefragments of SEQ ID NO: 2 that have alpha-glucosidase activity.

The present invention also relates to mutant polynucleotides comprisingat least one mutation in the mature polypeptide coding sequence of SEQID NO: 1, in which the mutant nucleotide sequence encodes a polypeptidewhich consists of amino acids 21 to 960 of SEQ ID NO: 2.

The techniques used to isolate or clone a polynucleotide encoding apolypeptide are known in the art and include isolation from genomic DNA,preparation from cDNA, or a combination thereof. The cloning of thepolynucleotides of the present invention from such genomic DNA can beeffected, e.g., by using the well known polymerase chain reaction (PCR)or antibody screening of expression libraries to detect cloned DNAfragments with shared structural features. See, e.g., Innis et al.,1990, PCR: A Guide to Methods and Application, Academic Press, New York.Other nucleic acid amplification procedures such as ligase chainreaction (LCR), ligated activated transcription (LAT) and nucleotidesequence-based amplification (NASBA) may be used. The polynucleotidesmay be cloned from a cell of Aspergillus, or another or related organismand thus, for example, may be an allelic or species variant of thepolypeptide encoding region of the nucleotide sequence.

The present invention also relates to polynucleotides having nucleotidesequences which have a degree of identity to the mature polypeptidecoding sequence of SEQ ID NO: 1 (i.e., nucleotides 142 to 2943) of atleast 85%, preferably at least 90%, more preferably at least 95%, andmost preferably at least 97% identity, which encode an activepolypeptide.

Modification of a nucleotide sequence encoding a polypeptide of thepresent invention may be necessary for the synthesis of polypeptidessubstantially similar to the polypeptide. The term “substantiallysimilar” to the polypeptide refers to non-naturally occurring forms ofthe polypeptide. These polypeptides may differ in some engineered wayfrom the polypeptide isolated from its native source, e.g., artificialvariants that differ in specific activity, thermostability, pH optimum,or the like. The variant sequence may be constructed on the basis of thenucleotide sequence presented as the polypeptide encoding region of SEQID NO: 1, e.g., a subsequence thereof, and/or by introduction ofnucleotide substitutions which do not give rise to another amino acidsequence of the polypeptide encoded by the nucleotide sequence, butwhich correspond to the codon usage of the host organism intended forproduction of the enzyme, or by introduction of nucleotide substitutionswhich may give rise to a different amino acid sequence. See, e.g., Fordet al., 1991, Protein Expression and Purification 2: 95-107 for ageneral description of nucleotide substitution.

It will be apparent to those skilled in the art that such substitutionscan be made outside the regions critical to the function of the moleculeand still result in an active polypeptide. Amino acid residues essentialto the activity of the polypeptide encoded by an isolated polynucleotideof the invention, and therefore preferably not subject to substitution,may be identified according to procedures known in the art, such assite-directed mutagenesis or alanine-scanning mutagenesis (see, e.g.,Cunningham and Wells, 1989, Science 244: 1081-1085). In the lattertechnique, mutations are introduced at every positively charged residuein the molecule, and the resultant mutant molecules are tested foralpha-glucosidase activity to identify amino acid residues that arecritical to the activity of the molecule. Sites of substrate-enzymeinteraction can also be determined by analysis of the three-dimensionalstructure as determined by such techniques as nuclear magnetic resonanceanalysis, crystallography or photoaffinity labelling (see, e.g., de Voset al., 1992, Science 255: 306-312; Smith et al., 1992, Journal ofMolecular Biology 224: 899-904; Wodaver et al., 1992, FEBS Letters 309:59-64).

The present invention also relates to isolated polynucleotides encodinga polypeptide of the present invention, which hybridize under very lowstringency conditions, preferably low stringency conditions, morepreferably medium stringency conditions, more preferably medium-highstringency conditions, even more preferably high stringency conditions,and most preferably very high stringency conditions with (i) nucleotides61 to 2880 of SEQ ID NO: 1, (ii) the genomic DNA sequence comprisingnucleotides 61 to 2880 of SEQ ID NO: 1, or (iii) a complementary strandof (i) or (ii); or allelic variants and subsequences thereof (Sambrooket al., 1989, supra), as defined herein.

The present invention also relates to isolated polynucleotides obtainedby (a) hybridizing a population of DNA under very low, low, medium,medium-high, high, or very high stringency conditions with (i)nucleotides 61 to 2880 of SEQ ID NO: 1, (ii) the genomic DNA sequencecomprising nucleotides 61 to 2880 of SEQ ID NO: 1, or (iii) acomplementary strand of (i) or (ii); and (b) isolating the hybridizingpolynucleotide, which encodes a polypeptide having alpha-glucosidaseactivity.

Nucleic Acid Constructs

The present invention also relates to nucleic acid constructs comprisingan isolated polynucleotide of the present invention operably linked toone or more control sequences which direct the expression of the codingsequence in a suitable host cell under conditions compatible with thecontrol sequences.

An isolated polynucleotide encoding a polypeptide of the presentinvention may be manipulated in a variety of ways to provide forexpression of the polypeptide. Manipulation of the polynucleotide'ssequence prior to its insertion into a vector may be desirable ornecessary depending on the expression vector. The techniques formodifying polynucleotide sequences utilizing recombinant DNA methods arewell known in the art.

The control sequence may be an appropriate promoter sequence, anucleotide sequence which is recognized by a host cell for expression ofa polynucleotide encoding a polypeptide of the present invention. Thepromoter sequence contains transcriptional control sequences whichmediate the expression of the polypeptide. The promoter may be anynucleotide sequence which shows transcriptional activity in the hostcell of choice including mutant, truncated, and hybrid promoters, andmay be obtained from genes encoding extracellular or intracellularpolypeptides either homologous or heterologous to the host cell.

Examples of suitable promoters for directing the transcription of thenucleic acid constructs of the present invention, especially in abacterial host cell, are the promoters obtained from the E. coli lacoperon, Streptomyces coelicolor agarase gene (dagA), Bacillus subtilislevansucrase gene (sacB), Bacillus licheniformis alpha-amylase gene(amyL), Bacillus stearothermophilus maltogenic amylase gene (amyM),Bacillus amyloliquefaciens alpha-amylase gene (amyQ), Bacilluslicheniformis penicillinase gene (penP), Bacillus subtilis xylA and xylBgenes, and prokaryotic beta-lactamase gene (VIIIa-Kamaroff et al., 1978,Proceedings of the National Academy of Sciences USA 75: 3727-3731), aswell as the tac promoter (DeBoer et al., 1983, Proceedings of theNational Academy of Sciences USA 80: 21-25). Further promoters aredescribed in “Useful proteins from recombinant bacteria” in ScientificAmerican, 1980, 242: 74-94; and in Sambrook et al., 1989, supra.

Examples of suitable promoters for directing the transcription of thenucleic acid constructs of the present invention in a filamentous fungalhost cell are promoters obtained from the genes for Aspergillus oryzaeTAKA amylase, Rhizomucor miehei aspartic proteinase, Aspergillus nigerneutral alpha-amylase, Aspergillus niger acid stable alpha-amylase,Aspergillus niger or Aspergillus awamori glucoamylase (glaA), Rhizomucormiehei lipase, Aspergillus oryzae alkaline protease, Aspergillus oryzaetriose phosphate isomerase, Aspergillus nidulans acetamidase, Fusariumvenenatum amyloglucosidase (WO 00/56900), Fusarium venenatum Daria (WO00/56900), Fusarium venenatum Quinn (WO 00/56900), Fusarium oxysporumtrypsin-like protease (WO 96/00787), Trichoderma reeseibeta-glucosidase, Trichoderma reesei cellobiohydrolase I, Trichodermareesei endoglucanase I, Trichoderma reesei endoglucanase II, Trichodermareesei endoglucanase III, Trichoderma reesei endoglucanase IV,Trichoderma reesei endoglucanase V, Trichoderma reesei xylanase I,Trichoderma reesei xylanase II, Trichoderma reesei beta-xylosidase, aswell as the NA2-tpi promoter (a hybrid of the promoters from the genesfor Aspergillus niger neutral alpha-amylase and Aspergillus oryzaetriose phosphate isomerase); and mutant, truncated, and hybrid promotersthereof.

In a yeast host, useful promoters are obtained from the genes forSaccharomyces cerevisiae enolase (ENO-1), Saccharomyces cerevisiaegalactokinase (GAL1), Saccharomyces cerevisiae alcoholdehydrogenase/glyceraldehyde-3-phosphate dehydrogenase (ADH1,ADH2/GAP),Saccharomyces cerevisiae triose phosphate isomerase (TPI), Saccharomycescerevisiae metallothionine (CUP1), and Saccharomyces cerevisiae3-phosphoglycerate kinase. Other useful promoters for yeast host cellsare described by Romanos et al., 1992, Yeast 8: 423-488.

The control sequence may also be a suitable transcription terminatorsequence, a sequence recognized by a host cell to terminatetranscription. The terminator sequence is operably linked to the 3′terminus of the nucleotide sequence encoding the polypeptide. Anyterminator which is functional in the host cell of choice may be used inthe present invention.

Preferred terminators for filamentous fungal host cells are obtainedfrom the genes for Aspergillus oryzae TAKA amylase, Aspergillus nigerglucoamylase, Aspergillus nidulans anthranilate synthase, Aspergillusniger alpha-glucosidase, and Fusarium oxysporum trypsin-like protease.

Preferred terminators for yeast host cells are obtained from the genesfor Saccharomyces cerevisiae enolase, Saccharomyces cerevisiaecytochrome C (CYC1), and Saccharomyces cerevisiaeglyceraldehyde-3-phosphate dehydrogenase. Other useful terminators foryeast host cells are described by Romanos et al., 1992, supra.

The control sequence may also be a suitable leader sequence, anontranslated region of an mRNA which is important for translation bythe host cell. The leader sequence is operably linked to the 5′ terminusof the nucleotide sequence encoding the polypeptide. Any leader sequencethat is functional in the host cell of choice may be used in the presentinvention.

Preferred leaders for filamentous fungal host cells are obtained fromthe genes for Aspergillus oryzae TAKA amylase and Aspergillus nidulanstriose phosphate isomerase.

Suitable leaders for yeast host cells are obtained from the genes forSaccharomyces cerevisiae enolase (ENO-1), Saccharomyces cerevisiae3-phosphoglycerate kinase, Saccharomyces cerevisiae alpha-factor, andSaccharomyces cerevisiae alcoholdehydrogenase/glyceraldehyde-3-phosphate dehydrogenase (ADH2/GAP).

The control sequence may also be a polyadenylation sequence, a sequenceoperably linked to the 3′ terminus of the nucleotide sequence and which,when transcribed, is recognized by the host cell as a signal to addpolyadenosine residues to transcribed mRNA. Any polyadenylation sequencewhich is functional in the host cell of choice may be used in thepresent invention.

Preferred polyadenylation sequences for filamentous fungal host cellsare obtained from the genes for Aspergillus oryzae TAKA amylase,Aspergillus niger glucoamylase, Aspergillus nidulans anthranilatesynthase, Fusarium oxysporum trypsin-like protease, and Aspergillusniger alpha-glucosidase.

Useful polyadenylation sequences for yeast host cells are described byGuo and Sherman, 1995, Molecular Cellular Biology 15: 5983-5990.

The control sequence may also be a signal peptide coding region thatcodes for an amino acid sequence linked to the amino terminus of apolypeptide and directs the encoded polypeptide into the cell'ssecretory pathway. The 5′ end of the coding sequence of the nucleotidesequence may inherently contain a signal peptide coding region naturallylinked in translation reading frame with the segment of the codingregion which encodes the secreted polypeptide. Alternatively, the 5′ endof the coding sequence may contain a signal peptide coding region whichis foreign to the coding sequence. The foreign signal peptide codingregion may be required where the coding sequence does not naturallycontain a signal peptide coding region. Alternatively, the foreignsignal peptide coding region may simply replace the natural signalpeptide coding region in order to enhance secretion of the polypeptide.However, any signal peptide coding region which directs the expressedpolypeptide into the secretory pathway of a host cell of choice may beused in the present invention.

Effective signal peptide coding regions for bacterial host cells are thesignal peptide coding regions obtained from the genes for Bacillus NCIB11837 maltogenic amylase, Bacillus stearothermophilus alpha-amylase,Bacillus licheniformis subtilisin, Bacillus licheniformisbeta-lactamase, Bacillus stearothermophilus neutral proteases (nprT,nprS, nprM), and Bacillus subtilis prsA. Further signal peptides aredescribed by Simonen and Palva, 1993, Microbiological Reviews 57:109-137.

Effective signal peptide coding regions for filamentous fungal hostcells are the signal peptide coding regions obtained from the genes forAspergillus oryzae TAKA amylase, Aspergillus niger neutral amylase,Aspergillus niger glucoamylase, Rhizomucor miehei aspartic proteinase,Humicola insolens cellulase, and Humicola lanuginosa lipase.

In a preferred aspect, the signal peptide coding region is nucleotides 1to 141 of SEQ ID NO: 1 which encode amino acids 1 to 20 of SEQ ID NO: 2.

Useful signal peptides for yeast host cells are obtained from the genesfor Saccharomyces cerevisiae alpha-factor and Saccharomyces cerevisiaeinvertase. Other useful signal peptide coding regions are described byRomanos et al., 1992, supra.

The control sequence may also be a propeptide coding region that codesfor an amino acid sequence positioned at the amino terminus of apolypeptide. The resultant polypeptide is known as a proenzyme orpropolypeptide (or a zymogen in some cases). A propolypeptide isgenerally inactive and can be converted to a mature active polypeptideby catalytic or autocatalytic cleavage of the propeptide from thepropolypeptide. The propeptide coding region may be obtained from thegenes for Bacillus subtilis alkaline protease (aprE), Bacillus subtilisneutral protease (nprT), Saccharomyces cerevisiae alpha-factor,Rhizomucor miehei aspartic proteinase, and Myceliophthora thermophilalaccase (WO 95/33836).

Where both signal peptide and propeptide regions are present at theamino terminus of a polypeptide, the propeptide region is positionednext to the amino terminus of a polypeptide and the signal peptideregion is positioned next to the amino terminus of the propeptideregion.

It may also be desirable to add regulatory sequences which allow theregulation of the expression of the polypeptide relative to the growthof the host cell. Examples of regulatory systems are those which causethe expression of the gene to be turned on or off in response to achemical or physical stimulus, including the presence of a regulatorycompound. Regulatory systems in prokaryotic systems include the fac,tac, and trp operator systems. In yeast, the ADH2 system or GAL1 systemmay be used. In filamentous fungi, the TAKA alpha-amylase promoter,Aspergillus niger glucoamylase promoter, and Aspergillus oryzaeglucoamylase promoter may be used as regulatory sequences. Otherexamples of regulatory sequences are those which allow for geneamplification. In eukaryotic systems, these include the dihydrofolatereductase gene which is amplified in the presence of methotrexate, andthe metallothionein genes which are amplified with heavy metals. Inthese cases, the nucleotide sequence encoding the polypeptide would beoperably linked with the regulatory sequence.

Expression Vectors

The present invention also relates to recombinant expression vectorscomprising a polynucleotide of the present invention, a promoter, andtranscriptional and translational stop signals. The various nucleicacids and control sequences described above may be joined together toproduce a recombinant expression vector which may include one or moreconvenient restriction sites to allow for insertion or substitution ofthe nucleotide sequence encoding the polypeptide at such sites.Alternatively, a nucleotide sequence of the present invention may beexpressed by inserting the nucleotide sequence or a nucleic acidconstruct comprising the sequence into an appropriate vector forexpression. In creating the expression vector, the coding sequence islocated in the vector so that the coding sequence is operably linkedwith the appropriate control sequences for expression.

The recombinant expression vector may be any vector (e.g., a plasmid orvirus) which can be conveniently subjected to recombinant DNA proceduresand can bring about expression of the nucleotide sequence. The choice ofthe vector will typically depend on the compatibility of the vector withthe host cell into which the vector is to be introduced. The vectors maybe linear or closed circular plasmids.

The vector may be an autonomously replicating vector, i.e., a vectorwhich exists as an extrachromosomal entity, the replication of which isindependent of chromosomal replication, e.g., a plasmid, anextrachromosomal element, a minichromosome, or an artificial chromosome.The vector may contain any means for assuring self-replication.Alternatively, the vector may be one which, when introduced into thehost cell, is integrated into the genome and replicated together withthe chromosome(s) into which it has been integrated. Furthermore, asingle vector or plasmid or two or more vectors or plasmids whichtogether contain the total DNA to be introduced into the genome of thehost cell, or a transposon may be used.

The vectors of the present invention preferably contain one or moreselectable markers which permit easy selection of transformed cells. Aselectable marker is a gene the product of which provides for biocide orviral resistance, resistance to heavy metals, prototrophy to auxotrophs,and the like.

Examples of bacterial selectable markers are the dal genes from Bacillussubtilis or Bacillus licheniformis, or markers which confer antibioticresistance such as ampicillin, kanamycin, chloramphenicol, ortetracycline resistance. Suitable markers for yeast host cells are ADE2,HIS3, LEU2, LYS2, MET3, TRP1, and URA3. Selectable markers for use in afilamentous fungal host cell include, but are not limited to, amdS(acetamidase), argB (ornithine carbamoyltransferase), bar(phosphinothricin acetyltransferase), hph (hygromycinphosphotransferase), niaD (nitrate reductase), pyrG(orotidine-5′-phosphate decarboxylase), sC (sulfate adenyltransferase),and trpC (anthranilate synthase), as well as equivalents thereof.Preferred for use in an Aspergillus cell are the amdS and pyrG genes ofAspergillus nidulans or Aspergillus oryzae and the bar gene ofStreptomyces hygroscopicus.

The vectors of the present invention preferably contain an element(s)that permits integration of the vector into the host cell's genome orautonomous replication of the vector in the cell independent of thegenome.

For integration into the host cell genome, the vector may rely on thepolynucleotide's sequence encoding the polypeptide or any other elementof the vector for integration into the genome by homologous ornonhomologous recombination. Alternatively, the vector may containadditional nucleotide sequences for directing integration by homologousrecombination into the genome of the host cell at a precise location(s)in the chromosome(s). To increase the likelihood of integration at aprecise location, the integrational elements should preferably contain asufficient number of nucleic acids, such as 100 to 10,000 base pairs,preferably 400 to 10,000 base pairs, and most preferably 800 to 10,000base pairs, which have a high degree of identity with the correspondingtarget sequence to enhance the probability of homologous recombination.The integrational elements may be any sequence that is homologous withthe target sequence in the genome of the host cell. Furthermore, theintegrational elements may be non-encoding or encoding nucleotidesequences. On the other hand, the vector may be integrated into thegenome of the host cell by non-homologous recombination.

For autonomous replication, the vector may further comprise an origin ofreplication enabling the vector to replicate autonomously in the hostcell in question. The origin of replication may be any plasmidreplicator mediating autonomous replication which functions in a cell.The term “origin of replication” or “plasmid replicator” is definedherein as a nucleotide sequence that enables a plasmid or vector toreplicate in vivo.

Examples of bacterial origins of replication are the origins ofreplication of plasmids pBR322, pUC19, pACYC177, and pACYC184 permittingreplication in E. coli, and pUB110, pE194, pTA1060, and pAMβ1 permittingreplication in Bacillus.

Examples of origins of replication for use in a yeast host cell are the2 micron origin of replication, ARS1, ARS4, the combination of ARS1 andCEN3, and the combination of ARS4 and CEN6.

Examples of origins of replication useful in a filamentous fungal cellare AMA1 and ANS1 (Gems et al., 1991, Gene 98:61-67; Cullen et al.,1987, Nucleic Acids Research 15: 9163-9175; WO 00/24883). Isolation ofthe AMAL gene and construction of plasmids or vectors comprising thegene can be accomplished according to the methods disclosed in WO00/24883.

More than one copy of a polynucleotide of the present invention may beinserted into the host cell to increase production of the gene product.An increase in the copy number of the polynucleotide can be obtained byintegrating at least one additional copy of the sequence into the hostcell genome or by including an amplifiable selectable marker gene withthe polynucleotide where cells containing amplified copies of theselectable marker gene, and thereby additional copies of thepolynucleotide, can be selected for by cultivating the cells in thepresence of the appropriate selectable agent.

The procedures used to ligate the elements described above to constructthe recombinant expression vectors of the present invention are wellknown to one skilled in the art (see, e.g., Sambrook et al., 1989,supra).

Host Cells

The present invention also relates to recombinant host cells, comprisinga polynucleotide of the present invention, which are advantageously usedin the recombinant production of the polypeptides. A vector comprising apolynucleotide of the present invention is introduced into a host cellso that the vector is maintained as a chromosomal integrant or as aself-replicating extra-chromosomal vector as described earlier. The term“host cell” encompasses any progeny of a parent cell that is notidentical to the parent cell due to mutations that occur duringreplication. The choice of a host cell will to a large extent dependupon the gene encoding the polypeptide and its source.

The host cell may be a unicellular microorganism, e.g., a prokaryote, ora non-unicellular microorganism, e.g., a eukaryote.

Useful unicellular microorganisms are bacterial cells such as grampositive bacteria including, but not limited to, a Bacillus cell, e.g.,Bacillus alkalophilus, Bacillus amyloliquefaciens, Bacillus brevis,Bacillus circulans, Bacillus clausii, Bacillus coagulans, Bacilluslautus, Bacillus lentus, Bacillus licheniformis, Bacillus megaterium,Bacillus stearothermophilus, Bacillus subtilis, and Bacillusthuringiensis; or a Streptomyces cell, e.g., Streptomyces lividans andStreptomyces murinus, or gram negative bacteria such as E. coli andPseudomonas sp. In a preferred aspect, the bacterial host cell is aBacillus lentus, Bacillus licheniformis, Bacillus stearothermophilus, orBacillus subtilis cell. In another preferred aspect, the Bacillus cellis an alkalophilic Bacillus.

The introduction of a vector into a bacterial host cell may, forinstance, be effected by protoplast transformation (see, e.g., Chang andCohen, 1979, Molecular General Genetics 168: 111-115), using competentcells (see, e.g., Young and Spizizin, 1961, Journal of Bacteriology 81:823-829, or Dubnau and Davidoff-Abelson, 1971, Journal of MolecularBiology 56: 209-221), electroporation (see, e.g., Shigekawa and Dower,1988, Biotechniques 6: 742-751), or conjugation (see, e.g., Koehler andThorne, 1987, Journal of Bacteriology 169: 5771-5278).

The host cell may be a eukaryote, such as a mammalian, insect, plant, orfungal cell.

In a preferred aspect, the host cell is a fungal cell. “Fungi” as usedherein includes the phyla Ascomycota, Basidiomycota, Chytridiomycota,and Zygomycota (as defined by Hawksworth et al., In, Ainsworth andBisby's Dictionary of The Fungi, 8th edition, 1995, CAB International,University Press, Cambridge, UK) as well as the Oomycota (as cited inHawksworth et al., 1995, supra, page 171) and all mitosporic fungi(Hawksworth et al., 1995, supra).

In a more preferred aspect, the fungal host cell is a yeast cell.“Yeast” as used herein includes ascosporogenous yeast (Endomycetales),basidiosporogenous yeast, and yeast belonging to the Fungi Imperfecti(Blastomycetes). Since the classification of yeast may change in thefuture, for the purposes of this invention, yeast shall be defined asdescribed in Biology and Activities of Yeast (Skinner, F. A., Passmore,S. M., and Davenport, R. R., eds, Soc. App. Bacteriol. Symposium SeriesNo. 9, 1980).

In an even more preferred aspect, the yeast host cell is a Candida,Hansenula, Kluyveromyces, Pichia, Saccharomyces, Schizosaccharomyces, orYarrowia cell.

In a most preferred aspect, the yeast host cell is a Saccharomycescarlsbergensis, Saccharomyces cerevisiae, Saccharomyces diastaticus,Saccharomyces douglasii, Saccharomyces kluyveri, Saccharomyces norbensisor Saccharomyces oviformis cell. In another most preferred aspect, theyeast host cell is a Kluyveromyces lactis cell. In another mostpreferred aspect, the yeast host cell is a Yarrowia lipolytica cell.

In another more preferred aspect, the fungal host cell is a filamentousfungal cell. “Filamentous fungi” include all filamentous forms of thesubdivision Eumycota and Oomycota (as defined by Hawksworth et al.,1995, supra). The filamentous fungi are generally characterized by amycelial wall composed of chitin, cellulose, glucan, chitosan, mannan,and other complex polysaccharides. Vegetative growth is by hyphalelongation and carbon catabolism is obligately aerobic. In contrast,vegetative growth by yeasts such as Saccharomyces cerevisiae is bybudding of a unicellular thallus and carbon catabolism may befermentative.

In an even more preferred aspect, the filamentous fungal host cell is anAcremonium, Aspergillus, Aureobasidium, Bjerkandera, Ceriporiopsis,Coprinus, Coriolus, Cryptococcus, Filibasidium, Fusarium, Humicola,Magnaporthe, Mucor, Myceliophthora, Neocallimastix, Neurospora,Paecilomyces, Penicillium, Phanerochaete, Phlebia, Piromyces, Pleurotus,Schizophyllum, Talaromyces, Thermoascus, Thielavia, Tolypocladium,Trametes, or Trichoderma cell.

In a most preferred aspect, the filamentous fungal host cell is anAspergillus awamori, Aspergillus fumigatus, Aspergillus foetidus,Aspergillus japonicus, Aspergillus nidulans, Aspergillus niger orAspergillus oryzae cell. In another most preferred aspect, thefilamentous fungal host cell is a Fusarium bactridioides, Fusariumcerealis, Fusarium crookwellense, Fusarium culmorum, Fusariumgraminearum, Fusarium graminum, Fusarium heterosporum, Fusarium negundi,Fusarium oxysporum, Fusarium reticulatum, Fusarium roseum, Fusariumsambucinum, Fusarium sarcochroum, Fusarium sporotrichioides, Fusariumsulphureum, Fusarium torulosum, Fusarium trichothecioides, or Fusariumvenenatum cell. In another most preferred aspect, the filamentous fungalhost cell is a Bjerkandera adusta, Ceriponopsis aneirina, Ceriporiopsisaneirina, Ceriporiopsis caregiea, Ceriporiopsis gilvescens,Ceriporiopsis pannocinta, Ceriporiopsis rivulosa, Cerporiopsis subrufa,Ceriporiopsis subvermispora, Coprinus cinereus, Coriolus hirsutus,Humicola insolens, Humicola lanuginosa, Mucor miehei, Myceliophthorathermophila, Neurospora crassa, Penicillium purpurogenum, Phanerochaetechrysosporium, Phlebia radiata, Pleurotus eryngii, Thielavia terrestris,Trametes villosa, Trametes versicolor, Trichoderma harzianum,Trichoderma koningii, Trichoderma longibrachiatum, Trichoderma reesei,or Trichoderma viride cell.

Fungal cells may be transformed by a process involving protoplastformation, transformation of the protoplasts, and regeneration of thecell wall in a manner known per se. Suitable procedures fortransformation of Aspergillus and Trichoderma host cells are describedin EP 238 023 and Yelton et al., 1984, Proceedings of the NationalAcademy of Sciences USA 81: 1470-1474. Suitable methods for transformingFusarium species are described by Malardier et al., 1989, Gene 78:147-156, and WO 96/00787. Yeast may be transformed using the proceduresdescribed by Becker and Guarente, In Abelson, J. N. and Simon, M. I.,editors, Guide to Yeast Genetics and Molecular Biology, Methods inEnzymology, Volume 194, pp 182-187, Academic Press, Inc., New York; Itoet al., 1983, Journal of Bacteriology 153: 163; and Hinnen et al., 1978,Proceedings of the National Academy of Sciences USA 75: 1920.

Methods of Production

The present invention also relates to methods for producing apolypeptide of the present invention, comprising (a) cultivating a cell,which in its wild-type form is capable of producing the polypeptide,under conditions conducive for production of the polypeptide; and (b)recovering the polypeptide. Preferably, the cell is of the genusFusarium, and more preferably Fusarium venenatum.

The present invention also relates to methods for producing apolypeptide of the present invention, comprising (a) cultivating a hostcell under conditions conducive for production of the polypeptide; and(b) recovering the polypeptide.

The present invention also relates to methods for producing apolypeptide of the present invention, comprising (a) cultivating a hostcell under conditions conducive for production of the polypeptide,wherein the host cell comprises a mutant nucleotide sequence having atleast one mutation in the mature polypeptide coding region of SEQ ID NO:1, wherein the mutant nucleotide sequence encodes a polypeptide whichconsists of amino acids 21 to 960 of SEQ ID NO: 2, and (b) recoveringthe polypeptide.

In the production methods of the present invention, the cells arecultivated in a nutrient medium suitable for production of thepolypeptide using methods well known in the art. For example, the cellmay be cultivated by shake flask cultivation, and small-scale orlarge-scale fermentation (including continuous, batch, fed-batch, orsolid state fermentations) in laboratory or industrial fermentorsperformed in a suitable medium and under conditions allowing thepolypeptide to be expressed and/or isolated. The cultivation takes placein a suitable nutrient medium comprising carbon and nitrogen sources andinorganic salts, using procedures known in the art. Suitable media areavailable from commercial suppliers or may be prepared according topublished compositions (e.g., in catalogues of the American Type CultureCollection). If the polypeptide is secreted into the nutrient medium,the polypeptide can be recovered directly from the medium. If thepolypeptide is not secreted, it can be recovered from cell lysates.

The polypeptides may be detected using methods known in the art that arespecific for the polypeptides. These detection methods may include useof specific antibodies, formation of an enzyme product, or disappearanceof an enzyme substrate. For example, an enzyme assay may be used todetermine the activity of the polypeptide as described herein.

The resulting polypeptide may be recovered using methods known in theart. For example, the polypeptide may be recovered from the nutrientmedium by conventional procedures including, but not limited to,centrifugation, filtration, extraction, spray-drying, evaporation, orprecipitation.

The polypeptides of the present invention may be purified by a varietyof procedures known in the art including, but not limited to,chromatography (e.g., ion exchange, affinity, hydrophobic,chromatofocusing, and size exclusion), electrophoretic procedures (e.g.,preparative isoelectric focusing), differential solubility (e.g.,ammonium sulfate precipitation), SDS-PAGE, or extraction (see, e.g.,Protein Purifcation, J.-C. Janson and Lars Ryden, editors, VCHPublishers, New York, 1989).

Plants

The present invention also relates to a transgenic plant, plant part, orplant cell which has been transformed with a nucleotide sequenceencoding a polypeptide having alpha-glucosidase activity of the presentinvention so as to express and produce the polypeptide in recoverablequantities. The polypeptide may be recovered from the plant or plantpart. Alternatively, the plant or plant part containing the recombinantpolypeptide may be used as such for improving the quality of a food orfeed, e.g., improving nutritional value, palatability, and rheologicalproperties, or to destroy an antinutritive factor.

The transgenic plant can be dicotyledonous (a dicot) or monocotyledonous(a monocot). Examples of monocot plants are grasses, such as meadowgrass (blue grass, Poa), forage grass such as Festuca, Lolium, temperategrass, such as Agrostis, and cereals, e.g., wheat, oats, rye, barley,rice, sorghum, and maize (corn).

Examples of dicot plants are tobacco, legumes, such as lupins, potato,sugar beet, pea, bean and soybean, and cruciferous plants (familyBrassicaceae), such as cauliflower, rape seed, and the closely relatedmodel organism Arabidopsis thaliana.

Examples of plant parts are stem, callus, leaves, root, fruits, seeds,and tubers as well as the individual tissues comprising these parts,e.g., epidermis, mesophyll, parenchyme, vascular tissues, meristems.Specific plant cell compartments, such as chloroplasts, apoplasts,mitochondria, vacuoles, peroxisomes and cytoplasm are also considered tobe a plant part. Furthermore, any plant cell, whatever the tissueorigin, is considered to be a plant part. Likewise, plant parts such asspecific tissues and cells isolated to facilitate the utilisation of theinvention are also considered plant parts, e.g., embryos, endosperms,aleurone and seeds coats.

Also included within the scope of the present invention are the progenyof such plants, plant parts, and plant cells.

The transgenic plant or plant cell expressing a polypeptide of thepresent invention may be constructed in accordance with methods known inthe art. In short, the plant or plant cell is constructed byincorporating one or more expression constructs encoding a polypeptideof the present invention into the plant host genome and propagating theresulting modified plant or plant cell into a transgenic plant or plantcell.

The expression construct is conveniently a nucleic acid construct whichcomprises a polynucleotide encoding a polypeptide of the presentinvention operably linked with appropriate regulatory sequences requiredfor expression of the nucleotide sequence in the plant or plant part ofchoice. Furthermore, the expression construct may comprise a selectablemarker useful for identifying host cells into which the expressionconstruct has been integrated and DNA sequences necessary forintroduction of the construct into the plant in question (the latterdepends on the DNA introduction method to be used).

The choice of regulatory sequences, such as promoter and terminatorsequences and optionally signal or transit sequences is determined, forexample, on the basis of when, where, and how the polypeptide is desiredto be expressed. For instance, the expression of the gene encoding apolypeptide of the present invention may be constitutive or inducible,or may be developmental, stage or tissue specific, and the gene productmay be targeted to a specific tissue or plant part such as seeds orleaves. Regulatory sequences are, for example, described by Tague etal., 1988, Plant Physiology 86: 506.

For constitutive expression, the 35S-CaMV, the maize ubiquitin 1, andthe rice actin 1 promoter may be used (Franck et al., 1980, Cell 21:285-294, Christensen et al., 1992, Plant Mo. Biol. 18: 675-689; Zhang etal., 1991, Plant Cell 3: 1155-1165). Organ-specific promoters may be,for example, a promoter from storage sink tissues such as seeds, potatotubers, and fruits (Edwards & Coruzzi, 1990, Ann. Rev. Genet. 24:275-303), or from metabolic sink tissues such as meristems (Ito et al.,1994, Plant Mol. Biol. 24: 863-878), a seed specific promoter such asthe glutelin, prolamin, globulin, or albumin promoter from rice (Wu etal., 1998, Plant and Cell Physiology 39: 885-889), a Vicia faba promoterfrom the legumin B4 and the unknown seed protein gene from Vicia faba(Conrad et al., 1998, Journal of Plant Physiology 152: 708-711), apromoter from a seed oil body protein (Chen et al., 1998, Plant and CellPhysiology 39: 935-941), the storage protein napA promoter from Brassicanapus, or any other seed specific promoter known in the art, e.g., asdescribed in WO 91/14772. Furthermore, the promoter may be a leafspecific promoter such as the rbcs promoter from rice or tomato (Kyozukaet al., 1993, Plant Physiology 102: 991-1000, the chlorella virusadenine methyltransferase gene promoter (Mitra and Higgins, 1994, PlantMolecular Biology 26: 85-93), or the aldP gene promoter from rice(Kagaya et al., 1995, Molecular and General Genetics 248: 668-674), or awound inducible promoter such as the potato pin2 promoter (Xu et al.,1993, Plant Molecular Biology 22: 573-588). Likewise, the promoter mayinducible by abiotic treatments such as temperature, drought, oralterations in salinity or induced by exogenously applied substancesthat activate the promoter, e.g., ethanol, oestrogens, plant hormonessuch as ethylene, abscisic acid, and gibberellic acid, and heavy metals.

A promoter enhancer element may also be used to achieve higherexpression of a polypeptide of the present invention in the plant. Forinstance, the promoter enhancer element may be an intron which is placedbetween the promoter and the nucleotide sequence encoding a polypeptideof the present invention. For instance, Xu et al., 1993, supra, disclosethe use of the first intron of the rice actin 1 gene to enhanceexpression.

The selectable marker gene and any other parts of the expressionconstruct may be chosen from those available in the art.

The nucleic acid construct is incorporated into the plant genomeaccording to conventional techniques known in the art, includingAgrobacterium-mediated transformation, virus-mediated transformation,microinjection, particle bombardment, biolistic transformation, andelectroporation (Gasser et al., 1990, Science 244: 1293; Potrykus, 1990,Bio/Technology 8: 535; Shimamoto et al., 1989, Nature 338: 274).

Presently, Agrobacterium tumefaciens-mediated gene transfer is themethod of choice for generating transgenic dicots (for a review, seeHooykas and Schilperoort, 1992, Plant Molecular Biology 19: 15-38) andcan also be used for transforming monocots, although othertransformation methods are often used for these plants. Presently, themethod of choice for generating transgenic monocots is particlebombardment (microscopic gold or tungsten particles coated with thetransforming DNA) of embryonic calli or developing embryos (Christou,1992, Plant Journal 2: 275-281; Shimamoto, 1994, Current OpinionBiotechnology 5: 158-162; Vasil et al., 1992, Bio/Technology 10:667-674). An alternative method for transformation of monocots is basedon protoplast transformation as described by Omirulleh et al., 1993,Plant Molecular Biology 21: 415-428.

Following transformation, the transformants having incorporated theexpression construct are selected and regenerated into whole plantsaccording to methods well-known in the art. Often the transformationprocedure is designed for the selective elimination of selection geneseither during regeneration or in the following generations by using, forexample, co-transformation with two separate T-DNA constructs or sitespecific excision of the selection gene by a specific recombinase.

The present invention also relates to methods for producing apolypeptide of the present invention comprising (a) cultivating atransgenic plant or a plant cell comprising a polynucleotide encoding apolypeptide having alpha-glucosidase activity of the present inventionunder conditions conducive for production of the polypeptide; and (b)recovering the polypeptide.

Removal or Reduction of Alpha-Glucosidase Activity

The present invention also relates to methods for producing a mutant ofa parent cell, which comprises disrupting or deleting a polynucleotidesequence, or a portion thereof, encoding a polypeptide of the presentinvention, which results in the mutant cell producing less of thepolypeptide than the parent cell when cultivated under the sameconditions.

The mutant cell may be constructed by reducing or eliminating expressionof a nucleotide sequence encoding a polypeptide of the present inventionusing methods well known in the art, for example, insertions,disruptions, replacements, or deletions. The nucleotide sequence to bemodified or inactivated may be, for example, the coding region or a partthereof essential for activity, or a regulatory element required for theexpression of the coding region. An example of such a regulatory orcontrol sequence may be a promoter sequence or a functional partthereof, i.e., a part that is sufficient for affecting expression of thenucleotide sequence. Other control sequences for possible modificationinclude, but are not limited to, a leader, polyadenylation sequence,propeptide sequence, signal peptide sequence, transcription terminator,and transcriptional activator.

Modification or inactivation of the nucleotide sequence may be performedby subjecting the parent cell to mutagenesis and selecting for mutantcells in which expression of the nucleotide sequence has been reduced oreliminated. The mutagenesis, which may be specific or random, may beperformed, for example, by use of a suitable physical or chemicalmutagenizing agent, by use of a suitable oligonucleotide, or bysubjecting the DNA sequence to PCR generated mutagenesis. Furthermore,the mutagenesis may be performed by use of any combination of thesemutagenizing agents.

Examples of a physical or chemical mutagenizing agent suitable for thepresent purpose include ultraviolet (UV) irradiation, hydroxylamine,N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), O-methyl hydroxylamine,nitrous acid, ethyl methane sulphonate (EMS), sodium bisulphite, formicacid, and nucleotide analogues.

When such agents are used, the mutagenesis is typically performed byincubating the parent cell to be mutagenized in the presence of themutagenizing agent of choice under suitable conditions, and screeningand/or selecting for mutant cells exhibiting reduced or no expression ofthe gene.

Modification or inactivation of the nucleotide sequence may beaccomplished by introduction, substitution, or removal of one or morenucleotides in the gene or a regulatory element required for thetranscription or translation thereof. For example, nucleotides may beinserted or removed so as to result in the introduction of a stop codon,the removal of the start codon, or a change in the open reading frame.Such modification or inactivation may be accomplished by site-directedmutagenesis or PCR generated mutagenesis in accordance with methodsknown in the art. Although, in principle, the modification may beperformed in vivo, i.e., directly on the cell expressing the nucleotidesequence to be modified, it is preferred that the modification beperformed in vitro as exemplified below.

An example of a convenient way to eliminate or reduce expression of anucleotide sequence by a cell is based on techniques of genereplacement, gene deletion, or gene disruption. For example, in the genedisruption method, a nucleic acid sequence corresponding to theendogenous nucleotide sequence is mutagenized in vitro to produce adefective nucleic acid sequence which is then transformed into theparent cell to produce a defective gene. By homologous recombination,the defective nucleic acid sequence replaces the endogenous nucleotidesequence. It may be desirable that the defective nucleotide sequencealso encodes a marker that may be used for selection of transformants inwhich the nucleotide sequence has been modified or destroyed. In aparticularly preferred embodiment, the nucleotide sequence is disruptedwith a selectable marker such as those described herein.

Alternatively, modification or inactivation of the nucleotide sequencemay be performed by established anti-sense techniques using a sequencecomplementary to the nucleotide sequence. More specifically, expressionof the nucleotide sequence by a cell may be reduced or eliminated byintroducing a sequence complementary to the nucleotide sequence of thegene that may be transcribed in the cell and is capable of hybridizingto the mRNA produced in the cell. Under conditions allowing thecomplementary anti-sense nucleotide sequence to hybridize to the mRNA,the amount of protein translated is thus reduced or eliminated.

The present invention further relates to a mutant cell of a parent cellwhich comprises a disruption or deletion of a nucleotide sequenceencoding the polypeptide or a control sequence thereof, which results inthe mutant cell producing less of the polypeptide than the parent cell.

The polypeptide-deficient mutant cells so created are particularlyuseful as host cells for the expression of homologous and/orheterologous polypeptides. Therefore, the present invention furtherrelates to methods for producing a homologous or heterologouspolypeptide comprising (a) cultivating the mutant cell under conditionsconducive for production of the polypeptide; and (b) recovering thepolypeptide. The term “heterologous polypeptides” is defined herein aspolypeptides which are not native to the host cell, a native protein inwhich modifications have been made to alter the native sequence, or anative protein whose expression is quantitatively altered as a result ofa manipulation of the host cell by recombinant DNA techniques.

In a further aspect, the present invention relates to a method forproducing a protein product essentially free of alpha-glucosidaseactivity by fermentation of a cell which produces both a polypeptide ofthe present invention as well as the protein product of interest byadding an effective amount of an agent capable of inhibitingalpha-glucosidase activity to the fermentation broth before, during, orafter the fermentation has been completed, recovering the product ofinterest from the fermentation broth, and optionally subjecting therecovered product to further purification.

In a further aspect, the present invention relates to a method forproducing a protein product essentially free of alpha-glucosidaseactivity by cultivating the cell under conditions permitting theexpression of the product, subjecting the resultant culture broth to acombined pH and temperature treatment so as to reduce thealpha-glucosidase activity substantially, and recovering the productfrom the culture broth. Alternatively, the combined pH and temperaturetreatment may be performed on an enzyme preparation recovered from theculture broth. The combined pH and temperature treatment may optionallybe used in combination with a treatment with a alpha-glucosidaseinhibitor.

In accordance with this aspect of the invention, it is possible toremove at least 60%, preferably at least 75%, more preferably at least85%, still more preferably at least 95%, and most preferably at least99% of the alpha-glucosidase activity. Complete removal ofalpha-glucosidase activity may be obtained by use of this method.

The combined pH and temperature treatment is preferably carried out at apH in the range of 4-5 and a temperature in the range of 70-80° C. for asufficient period of time to attain the desired effect, where typically,30 to 60 minutes is sufficient.

The methods used for cultivation and purification of the product ofinterest may be performed by methods known in the art.

The methods of the present invention for producing an essentiallyalpha-glucosidase-free product is of particular interest in theproduction of eukaryotic polypeptides, in particular fungal proteinssuch as enzymes. The enzyme may be selected from, e.g., an amylolyticenzyme, lipolytic enzyme, proteolytic enzyme, cellulytic enzyme,oxidoreductase, or plant cell-wall degrading enzyme. Examples of suchenzymes include an aminopeptidase, amylase, amyloglucosidase,carbohydrase, carboxypeptidase, catalase, cellulase, chitinase,cutinase, cyclodextrin glycosyltransferase, deoxyribonuclease, esterase,galactosidase, beta-galactosidase, glucoamylase, glucose oxidase,glucosidase, haloperoxidase, hemicellulase, invertase, isomerase,laccase, ligase, lipase, lyase, mannosidase, oxidase, pectinolyticenzyme, peroxidase, phytase, phenoloxidase, polyphenoloxidase,proteolytic enzyme, ribonuclease, transferase, transglutaminase, orxylanase. The alpha-glucosidase-deficient cells may also be used toexpress heterologous proteins of pharmaceutical interest such ashormones, growth factors, receptors, and the like.

It will be understood that the term “eukaryotic polypeptides” includesnot only native polypeptides, but also those polypeptides, e.g.,enzymes, which have been modified by amino acid substitutions, deletionsor additions, or other such modifications to enhance activity,thermostability, pH tolerance and the like.

In a further aspect, the present invention relates to a protein productessentially free from alpha-glucosidase activity which is produced by amethod of the present invention.

Compositions

The present invention also relates to compositions comprising apolypeptide of the present invention. Preferably, the compositions areenriched in such a polypeptide. The term “enriched” indicates that thealpha-glucosidase activity of the composition has been increased, e.g.,with an enrichment factor of 1.1.

The composition may comprise a polypeptide of the present invention asthe major enzymatic component, e.g., a mono-component composition.Alternatively, the composition may comprise multiple enzymaticactivities, such as an aminopeptidase, amylase, carbohydrase,carboxypeptidase, catalase, cellulase, chitinase, cutinase, cyclodextringlycosyltransferase, deoxyribonuclease, esterase, alpha-galactosidase,beta-galactosidase, glucoamylase, alpha-glucosidase, beta-glucosidase,hatoperoxidase, invertase, laccase, lipase, mannosidase, oxidase,pectinolytic enzyme, peptidoglutaminase, peroxidase, phytase,polyphenoloxidase, proteolytic enzyme, ribonuclease, transglutaminase,or xylanase. The additional enzyme(s) may be produced, for example, by amicroorganism belonging to the genus Aspergillus, preferably Aspergillusaculeatus, Aspergillus awamori, Aspergillus fumigatus, Aspergillusfoetidus, Aspergillus japonicus, Aspergillus nidulans, Aspergillusniger, or Aspergillus oryzae; Fusarium, preferably Fusariumbactridioides, Fusarium cerealis, Fusarium crookwellense, Fusariumculmorum, Fusarium graminearum, Fusarium graminum, Fusariumheterosporum, Fusarium negundi, Fusarium oxysporum, Fusariumreticulatum, Fusarium roseum, Fusarium sambucinum, Fusarium sarcochroum,Fusarium sulphureum, Fusarium toruloseum, Fusarium trichothecioides, orFusarium venenatum; Humicola, preferably Humicola insolens or Humicolalanuginosa; or Trichoderma, preferably Trichoderma harzianum,Trichoderma koningii, Trichoderma longibrachiatum, Trichoderma reesei,or Trichoderma viride.

The polypeptide compositions may be prepared in accordance with methodsknown in the art and may be in the form of a liquid or a drycomposition. For instance, the polypeptide composition may be in theform of a granulate or a microgranulate. The polypeptide to be includedin the composition may be stabilized in accordance with methods known inthe art.

Examples are given below of preferred uses of the polypeptidecompositions of the invention. The dosage of the polypeptide compositionof the invention and other conditions under which the composition isused may be determined on the basis of methods known in the art.

Uses

The present invention is also directed to methods for using thepolypeptides having alpha-glucosidase activity.

The polypeptides of the present invention may be used in the productionof alcohol from cereal grains according to DE 2944483.

The polypeptides of the present invention may also be used to producefermented malt drinks, e.g., (low-caloric) beer, according to WO2002/55652 (published U.S. Patent Application 20040101591). Fermentedmalt beverages with reinforced filling taste and fullness of mouthfeelcan be produced by addition of a polypeptide having alpha-glucosidaseactivity prior to heat treatment in a wort production process in thecourse of manufacturing fermented malt beverages. Low-calorie beers canbe manufactured in which a polypeptide having alpha-glucosidase activityis added in the fermentation process in the brewing of beer. Productionof acetic acid can be reduced by addition of a polypeptide havingalpha-glucosidase activity in the fermentation process in the highgravity brewing of beer.

In manufacturing beers, starch derived from ingredients including maltis hydrolyzed by hydrolases (e.g., alpha-amylase, beta-amylase) andfermentable sugars such as glucose, maltose, and maltotriose, which abrewer's yeast can metabolize, oligosaccharides larger thanmaltotetraose, and dextrin are produced. The fermentable sugars are thenmetabolized by brewer's yeast (or other yeast) and converted to variouscomponents of beer such as alcohol. Oligosaccharides larger thanmaltotetraose and dextrin may remain in the beer without beingmetabolized and may participate in filling taste and fullness ofmouthfeel of the beverages.

In a preferred aspect, the method relates to producing a fermented maltbeverage, wherein a polypeptide having alpha-glucosidase activity of thepresent invention is added prior to heat treatment of wort in a wortproduction process for manufacturing a fermented malt beverage. Inanother more preferred aspect, the amount of the polypeptide havingalpha-glucosidase activity used is 50-400 ppm per the amount of themalt. In another preferred aspect, the polypeptide havingalpha-glucosidase activity is added simultaneously with ground malt. Inanother preferred aspect, the polypeptide having alpha-glucosidaseactivity is added to the mash prior to the heat treatment in the wortproduction process. In another preferred aspect, the polypeptide havingalpha-glucosidase activity is added in the malting process. In anotherpreferred aspect, only malt is used as an ingredient. In anotherpreferred aspect, malt and adjuncts are used as sugar ingredients.

In another preferred aspect, the method relates to producing a beer,wherein a polypeptide having alpha-glucosidase activity of the presentinvention is added to the fermentation process in the brewing of thebeer. In a more preferred aspect, the beer is a low-calorie beer orlight beer. In another preferred aspect, the addition of the polypeptidehaving alpha-glucosidase activity reduces acetic acid production. Inanother more preferred aspect, the concentration of original extract ofwort is over 10 and not more than 30 weight %. In another more preferredaspect, the amount of the polypeptide having alpha-glucosidase activityused is 50-400 ppm per the amount of the malt.

Signal Peptide

The present invention also relates to nucleic acid constructs comprisinga gene encoding a protein operably linked to a nucleotide sequenceconsisting of nucleotides 61 to 2880 of SEQ ID NO: 1 encoding a signalpeptide consisting of amino acids 1 to 20 of SEQ ID NO: 2, wherein thegene is foreign to the nucleotide sequence.

The present invention also, relates to recombinant expression vectorsand recombinant host cells comprising such nucleic acid constructs.

The present invention also relates to methods for producing a proteincomprising (a) cultivating such a recombinant host cell under conditionssuitable for production of the protein; and (b) recovering the protein.

The protein may be native or heterologous to a host cell. The term“protein” is not meant herein to refer to a specific length of theencoded product and, therefore, encompasses peptides, oligopeptides, andproteins. The term “protein” also encompasses two or more polypeptidescombined to form the encoded product. The proteins also include hybridpolypeptides which comprise a combination of partial or completepolypeptide sequences obtained from at least two different proteinswherein one or more may be heterologous or native to the host cell.Proteins further include naturally occurring allelic and engineeredvariations of the above mentioned proteins and hybrid proteins.

Preferably, the protein is a hormone or variant thereof, enzyme,receptor or portion thereof, antibody or portion thereof, or reporter.In a more preferred aspect, the protein is an oxidoreductase,transferase, hydrolase, lyase, isomerase, or ligase. In an even morepreferred aspect, the protein is an aminopeptidase, amylase,carbohydrase, carboxypeptidase, catalase, cellulase, chitinase,cutinase, cyclodextrin glycosyltransferase, deoxyribonuclease, esterase,alpha-galactosidase, beta-galactosidase, glucoamylase,alpha-glucosidase, beta-glucosidase, invertase, laccase, lipase,mannosidase, mutanase, oxidase, pectinolytic enzyme, peroxidase,phytase, polyphenoloxidase, proteolytic enzyme, ribonuclease,transglutaminase or xylanase.

The gene may be obtained from any prokaryotic, eukaryotic, or othersource.

The present invention is further described by the following exampleswhich should not be construed as limiting the scope of the invention.

EXAMPLES Materials

Chemicals used as buffers and substrates were commercial products of atleast reagent grade.

Fungal Strains

Fusanium venenatum strain WTY842-1-11 (Δtdi5, amdS⁺) was used forexpression of the Fusanium venenatum GH31 alpha-glucosidase gene.

Media and Solutions

RA Sporulation medium was composed per liter of 1 g of glucose, 50 g ofsuccinic acid, 12.1 g of NaNO₃, and 20 ml of 50× Vogel's salts (no C, noN).

50× Vogel's salts (no C, no N) was composed per liter of 250 g ofKH₂PO₄, 10 g of MgSO₄.7H₂O, 5 g of CaCl₂.2H₂O, 2.5 ml of biotinsolution, and 5 ml of Vogel's trace elements.

50× Vogel's trace elements solution was composed per liter of 50 g ofcitric acid, 50 g of ZnSO₄.7H₂O, 10 g of Fe(NH₄)₂(SO₄)₂₋₆H₂O, 2.5 g ofCuSO₄.5H₂O, 0.5 g of MnSO₄.H₂O, 0.5 g of H₃BO3, and 0.5 g ofNa₂MoO₄.2H₂O.

YPG medium was composed per liter of 1% yeast extract, 2% bactopeptone,and 5% glucose.

Vogel's NO₃ Regeneration Low-Melt medium was composed per liter of 20 mlof 50× Vogels solution with 25 mM NaNO₃ stock, 0.8 M sucrose and 1.5%low melting agarose (Sigma Chemical Company, St. Louis, Mo.).

50× Vogels solution with 25 mM NaNO₃ stock was compassed of per liter of125 g of sodium citrate, 250 g of KH₂PO₄, 106.25 g of NaNO₃, 10 g ofMgSO₄.7H₂O, 5 g of CaCl₂.2H₂O, 2.5 g of biotin solution, and 5 ml of 50×Vogels trace element solution.

Vogel's NO₃+BASTA (6 mg/ml) medium was composed per liter of 25 g ofsucrose, 25 g of Noble agar, 20 ml of 50× Vogel's salts with 25 mM NaNO₃stock, and 6 g of BASTA per liter.

M400 medium was composed per liter of 50 g of maltodextrin, 2 g ofMgSO₄.7H₂O, 2 g of KH₂PO₄, 4 g of citric acid, 8 g of yeast extract, 2 gof urea, 0.5 g of CaCl₂, and 0.5 ml of AMG trace metals solution.

AMG trace metals solution was composed per liter of 14.3 g ofZnSO₄.7H₂O, 2.5 g of CuSO₄.5H₂O, 0.5 g of NiCl₂.6H₂O, 13.8 g ofFeSO₄.7H₂O, 8.5 g of MnSO₄.H₂O, and 3 g of citric acid.

50× Vogel's salts solution was composed per liter of 125 g of sodiumcitrate, 250 g of KH₂PO₄, 10 g of MgSO₄.7H₂O, 5 g of CaCl₂.2H₂O, 2.5 mlof biotin stock solution, and 5 ml of 200×AMG Trace Elements Solution.

Biotin stock solution was composed of 5 mg of biotin in 100 ml of 50%ethanol.

200×AMG Trace Metals was composed per liter of 3 g of citric acid, 14.3g of ZnSO₄.7H₂O, 2.5 g of CuSO₄.5H₂O, 13.8 g of FeSO₄.7H₂O, and 8.5 g ofMnSO₄.H₂O.

Vogel's Salts medium was composed per liter of 20 ml of filtersterilized (0.2 μm diameter pore size, Fisher Millipore) 50× Vogel'ssalts solution, 16.5 g of monobasic ammonium phosphate, and 50 g ofsucrose, pH buffered to 6.50 using 5N NaOH prior to autoclaving for 25minutes. Prior to inoculation, when the solution had cooled, 2.5 mlBASTA were added from a filter sterilized 250 mg/ml stock solution for afinal concentration of 6 mg/ml.

SY50 medium was composed per liter of 50 g of sucrose, 2 g ofMgSO₄.7H₂O, 10 g of KH₂PO₄, 2 g of K₂SO₄, 2 g of citric acid.H₂O, 10 gof yeast extract, 2 g of urea, 0.5 g of CaCl₂.2H₂O, and 0.5 ml of200×AMG trace metals solution; adjusted pH to 6.00 with 5 N NaOH priorto autoclaving for 25 minutes.

STC was composed of 0.8 M sorbitol, 50 mM CaCl₂, and 25 mM Tris-Cl, pH8.

SPTC was composed of 0.8 M sorbitol, 25 mM Tris-HCl, pH 8, 50 mM CaCl₂,and 40% PEG 4000.

TBE buffer was composed of 50 mM Tris Base, 50 mM boric acid, and 1 mMdisodium EDTA.

Example 1 Production of Fusarium venenatum Mycelial Tissue

Fusarium venenatum CC1-3, a morphological mutant of Fusarium strain(NRRL 30747 or ATCC 20334) (Wiebe et al., 1991, Mycological Research 95:1284-1288), was grown in a two-liter lab-scale fermentor using afed-batch fermentation scheme with NUTRIOSE™ (Roquette Freres, S. A.,Beinheim, France) as the carbon source and yeast extract. Ammoniumphosphate was provided in the feed. The pH was maintained at 6 to 6.5,and the temperature was kept at 30° C. with positive dissolved oxygen.

Mycelial samples were harvested at 4 days post-inoculum and quick-frozenin liquid nitrogen. The samples were stored at −80° C. until they weredisrupted for RNA extraction.

Example 2 cDNA Library Construction

Total cellular RNA was extracted from the mycelial samples described inExample 1 according to the method of Timberlake and Barnard (1981, Cell26: 2937), and the RNA samples were analyzed by Northern hybridizationafter blotting from 1% formaldehyde-agarose gels (Davis et al., 1986,Basic Methods in Molecular Biology, Elsevier Science Publishing Co.,Inc., New York). Polyadenylated mRNA fractions were isolated from totalRNA with an mRNA Separator Kit™ (Clontech Laboratories, Inc., Palo Alto,Calif.) according to the manufacturer's instructions. Double-strandedcDNA was synthesized using approximately 5 μg of poly(A)+ mRNA accordingto the method of Gubler and Hoffman (1983, Gene 25: 263-269) except aNot I-(dT)18 primer (Pharmacia Biotech, Inc., Piscataway, N.J.) was usedto initiate first strand synthesis. The cDNA was treated with mung beannuclease (Boehringer Mannheim Corporation, Indianapolis, Ind.) and theends were made blunt with T4 DNA polymerase (New England Biolabs,Beverly, Mass.).

The cDNA was digested with Not I, size selected by agarose gelelectrophoresis (ca. 0.7-4.5 kb), and ligated with pZErO-2.1(Invitrogen, Carlsbad, Calif.) which had been cleaved with Not I plusEco RV and dephosphorylated with calf-intestine alkaline phosphatase(Boehringer Mannheim Corporation, Indianapolis, Ind.). The ligationmixture was used to transform competent E. coli TOP10 cells (Invitrogen,Carlsbad, Calif.). Transformants were selected on 2YT agar plates(Miller, 1992, A Short Course in Bacterial Genetics. A Laboratory Manualand Handbook for Escherichia coli and Related Bacteria, Cold SpringHarbor Press, Cold Spring Harbor, N.Y.) which contained kanamycin at afinal concentration of 50 μg/ml.

A directional cDNA library was constructed using the plasmid cloningvector pZErO-2.1. Library D was made using mRNA from mycelia harvestedat four days and cDNA library was amplified. The library was plated,titered, and independent clones were analyzed by DNA sequencing.

Library D consisted of about 7.5×10⁴ independent clones beforeamplication. Miniprep DNA was isolated from forty colonies in eachlibrary and checked for the presence and size of cDNA inserts. In thisanalysis 39 of 40 colonies (97.5%) from Library D contained inserts withsizes ranging from 600 bp to 2200 bp (avg.=1050 bp)

Example 3 Template Preparation and Nucleotide Sequencing

From the cDNA library described in Example 2, 1152 transformant colonieswere picked directly from the transformation plates into 96-wellmicrotiter dishes which contained 200 μl of 2YT broth (Miller, 1992,supra) with 50 μg/ml kanamycin. The plates were incubated overnight at37° C. without shaking. After incubation 100 μl of sterile 50% glycerolwere added to each well. The transformants were replicated intosecondary, deep-dish 96-well microculture plates (Advanced GeneticTechnologies Corporation, Gaithersburg, Md.) containing 1 ml ofMagnificent Broth™ (MacConnell Research, San Diego, Calif.) supplementedwith 50 μg of kanamycin per ml in each well. The primary microtiterplates were stored frozen at −80° C. The secondary deep-dish plates wereincubated at 37° C. overnight with vigorous agitation (300 rpm) onrotary shaker. To prevent spilling and cross-contamination, and to allowsufficient aeration, each secondary culture plate was covered with apolypropylene pad (Advanced Genetic Technologies Corporation,Gaithersburg, Md.) and a plastic microtiter dish cover.

DNA was isolated from each well using the 96-well Miniprep Kit protocolof Advanced Genetic Technologies Corporation (Gaithersburg, Md.) asmodified by Utterback et al. (1995, Genome Sci. Technol. 1:1-8).Single-pass DNA sequencing was done with a Perkin-Elmer AppliedBiosystems Model 377 XL Automatic DNA Sequencer (Perkin-Elmer AppliedBiosystems, Inc., Foster City, Calif.) using dye-terminator chemistry(Giesecke et al., 1992, Journal of Virology Methods 38: 47-60) and thereverse lac sequencing primer.

Example 4 Analysis of DNA Sequence Data

Nucleotide sequence data were scrutinized for quality, and samplesgiving improper spacing less than or equal to 9.2 or ambiguity levelsexceeding 3% were discarded or re-run. Vector sequences were trimmedwith assistance of FACTURA™ software (Perkin-Elmer Applied Biosystems,Inc., Foster City, Calif.). In addition, sequences were truncated at theend of each sample when the number of ambiguous base calls increased.All sequences were compared to each other to construct overlappingcontigs using TIGR Assembler software (Sutton, G. G. et al., 1995,Genome Science and Technology 1: 9019) to determine multiplicity ofvarious cDNA species represented in each library. Lastly, all sequenceswere translated in three frames and searched against a non-redundantdata base (NRDB) using GeneAssist™ software (Perkin-Elmer AppliedBiosystems, Inc., Foster City, Calif.) with a modified Smith-Watermanalgorithm using the BLOSUM 62 matrix with a threshold score of 70. TheNRDB was assembled from Genpept, Swiss-Prot, and PIR databases.

Example 5 Identification of Alpha-Glucosidase cDNA Clones

Putative alpha-glucosidase clones were identified by partial sequencingof random cDNA clones using an Applied Biosystems Model 377 XL AutomatedDNA Sequencer according to the manufacturer's instructions andcomparison of the deduced amino acid sequence to the sequences in theNRDB as described in Example 4. From the 1152 cDNA sequences analyzed,eleven clones from Library D showed amino acid sequence homology toalpha-glucosidase proteins from other fungi and yeasts. Among severalalpha-glucosidase cDNA clones discovered in this manner, two wereestimated to be full-length (encoding the complete protein) on the basisof its alignment to the Neurospora crassa (SWALL accession numberQ872B7) and Aspergillus nidulans (SWALL accession number Q9C1S7)alpha-glucosidase amino acid sequences and the presence of a possiblesignal peptide, detected using the Signal-P computer program (Nielsen,et al., 1997, Protein Engineering 10:1-6). The clone designated E. coliFD11F2 containing plasmid pFD11F2 was selected for expression inFusarium venenatum (see Example 7). E. coli FD11F2 containing plasmidpFD11F2 was deposited with the Agricultural Research Service PatentCulture Collection, Northern Regional Research Center, 1815 UniversityStreet, Peoria, Ill., 61604, as NRRL B-30753, with a deposit date ofJul. 1, 2004.

Example 6 Isolation, Nucleotide Sequencing and Characterization of acDNA Segment Encoding Fusarium venenatum Alpha-Glucosidase

DNA sequencing of the cloned insert in pFD11F2 was done with an AppliedBiosystems Model 3700 Automated DNA Sequencer using dye-terminatorchemistry. Contiguous sequences were generated using a primer walkingstrategy and assembled using phred/phrap/consed (University ofWashington). The inserted sequence in pFD11F2 was sequenced to anaverage error rate of less than 1 base per 10,000 bases.

By comparing the cDNA sequence data to the contig of alpha-glucosidasecDNA sequences, it was determined that the cDNA segment encodingFusarium venenatum alpha-glucosidase contained an open reading frame of2880 bp encoding a polypeptide of 960 amino acids. The nucleotidesequence (SEQ ID NO: 1) and deduced amino acid sequence (SEQ ID NO: 2)are shown in FIGS. 1A and 1B. The G+C content of SEQ ID NO: 1 is 52.3%and of nucleotides 61 to 2880 of SEQ ID NO: 1 is 52.1%. Using theSignalP version 2.0 program (Nielsen et al., 1997, Protein Engineering10:1-6), a signal peptide of 20 residues was predicted. The predictedmature protein contains 960 amino acids with a molecular mass of 105.8kDa.

A comparative alignment of fungal alpha-glucosidase protein sequenceswas undertaken using the Clustal method (Higgins, 1989, CABIOS 5:151-153) using the LASERGENE™ MEGALIGN™ software (DNASTAR, Inc.,Madison, Wis.) with an identity table and the following multiplealignment parameters: Gap penalty of 10 and gap length penalty of 10.Pairwise alignment parameters were Ktuple=1, gap penalty=3, Windows=5,and diagonals=5. The alignment showed that the Fusarium venenatumalpha-glucosidase shares identity with the following alpha-glucosidasesfrom other fungi (percent identical residues in parentheses):Aspergillus nidulans accession number Q9C1S7 (77%), Neurospora crassaaccession number Q872B7 (53%), Acremonium implicatum accession numberBAD08418 (51%), Mucor javanicus accession number Q92442 (37%), andAspergillus niger accession number P56526 (31%).

Example 7 Construction of pEJG61

The Fusanium venenatum expression vector pEJG61 was generated bymodification of pSheB1 (U.S. Pat. No. 6,090,604). The modificationsincluded (a) changing the single Bsp LU11I site in pSheB1 bysite-directed mutagenesis (b) replacement of 930 bp of the Fusariumoxysporum trypsin promoter with 2.1 kilobases of the Fusarium venenatumglucoamylase promoter, and (c) introduction of a Bsp LU11I site afterthe Fusanium venenatum glucoamylase promoter.

Removal of the Bsp LU11I site within the pSheB1 sequence wasaccomplished using the QuikChange™ Site-Directed Mutagenesis Kit(Stratagene Cloning Systems, La Jolla, Calif.) according to themanufacturer's instruction with the following pairs of mutagenesisprimers:

5′-GCAGGAAAGAACAAGTGAGCAAAAGGC-3′ (SEQ ID NO: 3)5′-GCCTTTTGCTCACTTGTTCTTTCCTGC-3′ (SEQ ID NO: 4)This created pSheB1 intermediate 1.

Removal of 930 bp of the Fusarium oxysporum trypsin promoter wasaccomplished by digesting pSheB1 intermediate 1 (6,971 bp) with Stu Iand Pac I, subjecting the digest to electrophoresis on a 1% agarose gel,at 100 volts for one hour using TBE buffer, excising the 6,040 bp vectorfragment, and purifying the excised fragment with a Qiaquick GelPurification Kit (QIAGEN Inc., Valencia, Calif.). To introduce a new BspLU11I site, a linker was created using the following primers:

5′-dCCTACATGTTTAAT-3′ (SEQ ID NO: 5)      Bsp Lu11l 5′-dTAAACATGTAGG-3′(SEQ ID NO: 6)Each primer (2 μg each) was heated to 70° C. for 10 minutes and thencooled to room temperature over an hour. This linker was ligated intothe Stu I-Pac I digested pSheB1 intermediate 1 vector fragment, creatingpSheBI intermediate 2.

A 2.1 kilobase fragment of Fusarium venenatum genomic DNA 5 prime of theglucoamylase coding region (glucoamylase promotor) was isolated by PCRof plasmid pFAMG (WO 00/56900) containing Fusarium venenatum genomic DNAencoding the entire coding region for Fusarium venenatum glucoamylaseand 3,950 bp of upstream sequence. The primers used for PCR follow:

5′-AGGCCTCACCCATCTCAACAC-3′ (SEQ ID NO: 7) 5′-ACATGTTGGTGATAGCAGTGA-3′(SEQ ID NO: 8)

The PCR reaction (50 μl) was composed of 200 ng of pFAMG, 200 μM dNTPs,1 μM of the above primers, 1× reaction buffer, and 2.6 units of ExpandHigh Fidelity enzyme mix. The reactions were incubated using a MJResearch Thermocycler (MJ Research, Inc., Boston, Mass.) programmed for1 cycle 1 at 94° C. for 2 minutes; 10 cycles each at 94° C. for 15seconds, 60° C. for 30 seconds, and 72° C. for 2 minutes and 15 seconds;15 cycles each at 94° C. for 15 seconds, 60° C. for 30 seconds, and 72°C. for 2 minutes and 15 seconds with 5 seconds cycle elongation for eachsuccessive cycle; and 1 cycle at 72° C. for 7 minutes.

The PCR product was subjected to electrophoresis on a 1% agarose gel at100 volts for one hour using TBE buffer generating an expected band of2,108 bp. The 2,108 bp PCR product was excised from the agarose gel andpurified with a Qiaquick Gel Purification Kit (QIAGEN Inc., Valencia,Calif.). This fragment was cut with Stu I and Bsp LU11I, purified with aQiaquick Purification Kit (QIAGEN Inc., Valencia, Calif.), and ligatedinto Stu I-Bsp LU11I digested pSheBI intermediate 2 creating pEJG61(FIG. 2).

Example 8 Construction of Fusarium venenatum Alpha-GlucosidaseExpression Vectors

An InFusion Cloning Kit (BD Biosciences, Palo Alto, Calif.) was used toclone the PCR fragment containing the alpha-glucosidase gene directlyinto the expression vector, pEJG61, without the need for restrictiondigests and ligation. The cDNA clone was subjected to PCR amplificationusing gene-specific forward and reverse primers shown below. Boldletters represent coding sequence while underlined letters representadded Bsp LU11I and Pac I sites to the 5′ and 3′ ends of thealpha-glucosidase gene, respectively. The remaining sequence ishomologous to the insertion sites of pEJG61.

Primer 997154 (5′BspLU11I Fv a-GS): (SEQ ID NO: 9)5′-CACTGCTATCACCAACATGTTCTTCAAGAAGCTGCT-3′ Primer 997155 (3′ Pacl Fva-GS): (SEQ ID NO: 10) 5′-CCAACAAGGTATTTAATTAATCAGAAGAGATCCAC-3′

The PCR amplification was performed using an Expand High Fidelity PCRSystem (Roche, Indianapolis, Ind.) according to manufacturer'sinstructions. Each PCR reaction (50 μl) was composed of 200 ng of cDNAclone template, 200 μM dNTPs, 1 μM forward and reverse primers, 1×reaction buffer, and 2.6 units of Expand High Fidelity enzyme mix. Thereactions were incubated using a MJ Research Thermocycler programmed for1 cycle 1 at 94° C. for 2 minutes; 10 cycles each at 94° C. for 15seconds, 60° C. for 30 sec, and 72° C. for 1 minute and 15 seconds; 15cycles each at 94° C. for 15 seconds, 60° C. for 30 seconds, and 72° C.for 1 minutes and 15 seconds with 5 seconds cycle elongation for eachsuccessive cycle; and 1 cycle at 72° C. for 7 minutes. An aliquot ofeach PCR product was run on a 0.7% agarose gel using TBE buffergenerating expected bands of approximately 3 bp.

The PCR product was gel purified using a QIAquick Gel Extraction Kit(Qiagen Inc., Valencia, Calif.), and then cloned into the pEJG61expression vector using an InFusion Cloning Kit (BD Biosciences, PaloAlto, Calif.), resulting in plasmid pJLin163 (FIG. 3). The InFusionCloning reaction (50 μl) was composed of 1× InFusion Buffer (BDBiosciences, Palo Alto, Calif.), 1×BSA (BD Biosciences, Palo Alto,Calif.), 1 μl of Infusion enzyme (diluted 1:10), 100 ng of pEJG61digested with Bsp LU11I and Pac I, and 50 ng of the purified PCR productcontaining the alpha-glucosidase gene. The reaction was incubated atroom temperature for 30 minutes. Two μls of the reaction was used totransform E. coli Solopac Gold supercompetent cells (Stratagene, LaJolla, Calif.) according to the manufacturer's instructions. An E. colitransformant containing the pJLin163 plasmid was isolated and confirmedby sequence analysis using an Applied Biosystems Model 377 Sequencer XLusing dye-terminator chemistry.

Example 9 Transformation of pJLin163 into Fusarium venenatum WTY842-1-11

Spores of Fusarium venenatum strain WT-Y842-1-11 (Δtrichodiene synthase,amdS+) a mutant of Fusarium strain A3/5 (NRRL 30747 or ATCC 20334)(Wiebe et al., 1992, Mycological Research 96: 555-562; Wiebe et al.,1991, Mycological Research 95: 1284-1288; Wiebe et al., 1991,Mycological Research 96: 555-562), were generated by inoculating a flaskcontaining 100 ml of RA sporulation medium with 8 plugs from an agarplate and incubated at 27° C., 150 rpm for 24 hours, then 24 hours, 150rpm at 22° C. Spores were harvested by filtering culture throughMiracloth onto a Nalgene 0.2 μm filter. Wash spores twice with steriledistilled water, resuspended in a small volume of water, and thencounted using a hemocytometer.

Protoplasts were prepared by inoculating 100 ml of YPG medium with 2×10⁸spores of Fusarium venenatum WTY842-1-11 and incubating for 15 hours at18° C. and 150 rpm. The culture was filtered through Miracloth, washedonce with sterile distilled water and once with 1 M MgSO₄ andresuspended in 40 ml of 5 mg/ml of NOVOZYME 234 mM in 1 M MgSO₄.Cultures were incubated at 29° C. and 90 rpm until protoplasts formed. Avolume of 30 ml of 1 M sorbitol was added to the protoplast digest andthe mixture was centrifuged at 1500 rpm for 10 minutes. The pellet wasresuspended, washed twice with 1 M sorbitol, and centrifuged at 1500 rpmfor 10 minutes to pellet the protoplasts. Protoplasts were counted witha hemocytometer and resuspended in an 8:2:0.1 solution of STC:SPTC:DMSOto a final concentration of 5×10⁷ protoplasts/ml. The protoplasts werestored at −80° C., after controlled-rate freezing in a Nalgene Cryo 1°C. Freezing Container.

Two ml of protoplast suspension were added to 100 μg of pJLin163circular plasmid and 250 μg heparin in a 50 ml Falcon tube, mixed andincubated on ice for 30-minutes. Two hundred μl of SPTC was mixed gentlyinto the protoplast suspension and incubation was continued at roomtemperature for 10 minutes. Twenty ml of SPTC was mixed gently into theprotoplast suspension and incubation was continued at room temperaturefor 10 minutes. A 350 ml volume of molten Vogel's NO₃ RegenerationLow-Melt medium (cooled to 50° C.) was mixed with the protoplasts andthen 35 ml were plated onto 100 mm Petri plate containing 35 ml of theidentical medium plus 12 mg of BASTA™ per ml. Incubation was continuedat room temperature for 10 to 14 days. After 12 days, 21 transformantswere apparent. A mycelial fragment from the edge of each transformantwas transferred to plates containing Vogel's NO₃ Regeneration Low-Meltmedium+BASTA (6 mg/ml) medium. The plate was sealed in a plastic bag tomaintain moisture and incubated approximately one week at roomtemperature.

The transformants of Fusarium venenatum WTY842-1-11 were grown in 25 mlof M400 medium in a 125 ml shake flask. The cultures were incubated at28° C. and 200 rpm. On days 2, 4, and 6, culture supernatants wereharvested and assayed for alpha-glucosidase activity. Culturesupernatants were diluted in 0.1 M sodium acetate buffer pH 4.3 inseries from 0-fold to ⅓-fold to 1/9-fold. An AMG standard obtained fromNovozymes A/S, Bagsvaerd, Denmark, was diluted using 2-fold stepsstarting with a 0.033 AGU/ml concentration and ending with a 0.0042AGU/ml concentration in 0.1 M sodium acetate buffer pH 4.3. A total of100 μl of each dilution including standard was transferred to a 96-wellflat bottom plate. Fifty micro-liters of a 20 mg/ml maltose solution wasadded to each well then incubated at 25° C. for 180 minutes. Uponcompletion of the incubation step 100 μl of a 0.06 N NaOH solution wasadded to each well to quench the reaction. A total of 30 μl wastransferred from each well and placed into a new 96-well plate followedby the addition of 200 μl of liquid glucose (oxidase) reagent (PointeScientific, Inc, Lincoln Park, Mich., USA) to each well and incubated atambient temperature for 8 minutes. Upon completion of the incubation,the absorbance at 490 nm was measured for the 96 well plate using aSpectra Max 349 (Molecular Devices, Sunnyvale, Calif.). Sampleconcentrations were determined by extrapolation from the generatedstandard curve. The glucose content present in the medium was normalizedby independently measuring glucose in the sample broth by the LiquidGlucose Reagent without addition of maltose. The absorbance wassubtracted from the value from reagents in which maltose substrate wasadded.

All of the twenty transformants expressed alpha-glucosidase. The highestproducing transformant was transformant 13.1.G24. Expression peaked onday 6 (Fig.). Untransformed strain Fusanium venenatum WTY842-1-11 had nodetectable activity. Transformant 13.1.G24 strain was renamed asFusanium venenatum JLin725.

Example 10 Fermentation of Fusarium venenatum JLin725

Fusanium venenatum JLin725 was evaluated for its ability to producealpha-glucosidase by fermentation.

All fermentations were started in a 2-stage liquid seed. The first stagewas in 100 ml of Vogel's Salts medium in a 500 ml unbaffled plasticshake flask, capped with silicone sponge closures. The medium wascomposed per liter of 20 ml of filter sterilized (0.2 μm diameter poresize, Fisher Millipore) Vogel's salts stock solution (prepared at 50×final concentration), 16.5 g of monobasic ammonium phosphate, and 50 gof sucrose, pH buffered to 6.50 using 5N NaOH prior to autoclaving for25 minutes. Prior to inoculation, when the solution had cooled, 2.5 mlof BASTA were added from a filter sterilized 250 mg/ml stock solutionfor a final concentration of 6 mg/ml.

Shake flasks were then inoculated with an approximately 1 cm² plug cutfrom a fresh seven-day old agar culture plate. The flasks were thenincubated for approximately 72 hours at 200 rpm and 28° C.

Second stage seeds were also prepared in 500 ml shake flasks withsilicone sponge closures, using 100 ml of SY50 medium. Second stageseeds were inoculated with 0.3 ml of culture from the first stage seed.These seeds were then incubated at 28° C., 200 rpm for approximately 48hours.

Fed-batch fermentors were set up in Applikon 3 L jacketed glassbioreactors. The medium, made in tap water, was composed per liter of 20g of sucrose, 2 g of MgSO₄.7H₂O, 2 g of KH₂PO₄, 2 g of citric acid, 5.6g of (NH₄)₂HPO₄, 0.5 ml of 200×AMG Trace Metals, 0.5 g of CaCl₂.2H₂O,and 30 ml of a vitamin stock solution (0.15 g of thiamine HCl, 0.08 g ofriboflavin, 0.4 g nicotinic acid, 0.5 g calcium pantothenate, 0.005 g ofbiotin, 0.05 g of folic acid, 0.1 g of pyridoxal-HCl, in deionizedwater, mixed over heat and filtered through a 0.45 μm filter (Millipore,Bedford, Mass.)). This batch mixture was adjusted to pH 6.50 with 5 NNaOH.

A total of 20 g of soy concentrate was added separately to each tankprior to filling with 1800 ml of medium. The headplate was then looselyinstalled and moderate agitation commenced to thoroughly mix and wet thesoy powder. Approximately 0.9 ml of pluronic acid was also added at thistime to minimize foaming.

The feed was made up in 2 liter plastic bottles, consisting of 495 g ofmaltose and tap water to make the final mass 1500 g. Pluronic acid (1ml) was added prior to mixing.

The pH was controlled at 6.25+/−0.25 using 15% NH₄OH solution in atightly capped bottle, and 5 NH₃PO₄. Tanks were operated at 1200 rpmagitation and 1 vvm airflow, with temperature at 29° C.+/−1° C.Inoculation from the second stage seeds was with 50 ml of cultureaseptically transferred to a 60 ml syringe which was injected into thetank.

Feed was started after approximately 19 hours, after pH has dropped tothe bottom of the control band and then risen again to the top of thecontrol band, signifying depletion of batch nutrients. Feed is at aconstant 3.78 g/L-hr for the length of the fermentation. DOconcentration was maintained above 30%.

Example 11 Purification and Characterization of Fusarium venenatumAlpha-glucosidase

Alpha-glucosidase activity was measured using maltose as substrate.Samples of 25 μl were mixed with 375 μl of a 1.1% maltose solution in 50mM acetate buffer, pH 5.0. The mixture was incubated for 10 minutes at37° C. Then 100 μl of 1 M Tris was added and a portion of the resultingsolution was transferred to an Eppendorf tube and placed into boilingwater for 3-4 minutes to quench the enzymatic hydrolysis of maltose. Tomeasure the liberated glucose, a 20 μl aliquot was transferred to a wellof 96-well microplate and mixed with 200 μl of glucoseoxidase-horseradishperoxidase-2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid)diammonium salt solution (0.6 g/l glucose oxidase, 0.02 g/l horseradishperoxidase and 1.0 g/l 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonicacid) diammonium salt in 100 mM sodium phosphate pH 7.0). Afterincubation for 30 minutes at room temperature, the absorbance at 420 nmwas measured using a Spectra Max 349 (Molecular Devices, Sunnyvale,Calif.).

Protein concentration was measured using a BCA Protein Assay Reagent(Pierce, Rockford, Ill.) according to the manufacturer's instructions.

Fusarium venenatum alpha-glucosidase was purified from a fermentationbroth supernatant produced by cultivation of Fusarium venenatum strainWTY842-1-11 (Δtri5, amdS*) as described in Example 10.

The culture broth supernatant (approximately 0.45 liter) was prepared bycentrifugation of the whole fermentation broth, and then filtered usingNalgene Filterware equipped with a 0.22 mm filter, diluted with 100 mMTris-HCl pH 8.0 buffer, and concentrated using an Amicon SpiralUltrafiltration System equipped with a PM 10 ultrafiltration membrane.The final preparation had a pH of 8.0 and conductivity of 7.2 mS It wasloaded onto a 24×390 mm column containing approximately 200 ml ofQ-Sepharose, Big Beads (Pharmacia Biotech AB, Uppsala, Sweden)pre-equilibrated with 100 mM Tris-HCl pH 8.0 buffer. Protein withalpha-glucosidase activity was eluted with a 700 ml gradient from 0 to0.8 M NaCl in 50 100 mM Tris-HCl pH 8.0 buffer. Fractions withalpha-glucosidase activity were pooled, desalted using a PM 10 membrane,and equilibrated with 100 mM Tris-HCl pH 8.0 buffer.

The pooled solution was then loaded onto a 20 ml Pharmacia MonoQ Beadscolumn pre-equilibrated with 100 mM Tris-HCl pH 8.0 buffer. Fractionswith alpha-glucosidase activity were pooled, concentrated andequilibrated with 100 mM Tris-HCl pH 8.0 buffer, 1.7M (NH₄)₂SO₄.

Finally, the concentrated sample was loaded onto a Pharmacia PhenylSuperose 5/5 pre-packed 7×50 mm column (Pharmacia Biotech AB, Uppsala,Sweden) pre-equilibrated with 100 mM Tris-HCl pH 8.0 buffer, containing1.7M (NH₄)₂SO₄. Protein with alpha-glucosidase activity was then elutedwith a 300 ml gradient from 1.7 to 0 M (NH₄)₂SO₄ in 100 mM Tris-HCl pH8.0 buffer. Fractions containing alpha-glucosidase activity wereanalyzed by standard SDS-PAGE and native gel and then pooled.

TABLE 1 summarizes the purification of alpha-glucosidase. Table 1.Summary of Purification of Alpha-Glucosidase Volume Protein % Total (ml)(mg) activity¹ Initial supematant 775 891 100 Acetate wash onQ-Sepharose 250 95 82.3 (pigment removal) Q-Sepharose columnchromatography 264 32 82.3 MonoQ column chromatography 90 15 51.9 PhenylSuperose column 21 9 41.0 chromatography ¹Alpha-glucosidase activity wasmeasured at pH 5.0 using maltose as a substrate (AMG activity-assayprotocol. Maltose solution was preheated up to 37° C. The incubationwith the enzyme was done at room temperature).

A native gel (BioRad Precast Polyacrylamide Gel, Bio-Rad Laboratories,Inc., Hercules, Calif.) was run to determine whether the alpha-amylasewas composed of several subunits. The sample buffer was 4.0 ml of 0.5 MTris-HCl pH 8.8, 0.5 ml of 0.1% bromophenol blue, 2.0 ml of glycerol,and distilled water to 10.0 ml. The running buffer was composed perliter of 2.9 g of Tris Base and 14.4 g of glycine, adjusted to pH 8.3.The gel was run at 200 V for 1 hour and stained as described in Example9. The native gel showed only one band with a molecular weight around140 kDa, suggesting the enzyme was not composed of subunits.

pH optimum. Specific activity of the purified Fusarium venenatumalpha-glucosidase was measured at different pH values in 50 mM acetatebuffer/50 mM phosphate buffer at 37° C. using the activity assaydescribed above.

Fusarium venenatum alpha-glucosidase has pH optimum of activity as shownin FIG. 4 in the range of about 4.5 to about 6.0, preferably about 4.7to about 5.7, more preferably about 4.8 to about 5.5, most preferablyabout 5.0 to about 5.3, and even most preferably at pH 5.0.

Thermostability. The thermostability of the purified Fusarium venenatumalpha-glucosidase was determined by incubating the alpha-glucosidase in50 mM sodium acetate pH 5.0 for 5 minutes in a water bath at thefollowing temperatures: 35, 45, 50, 55, 60, 65, 71 and 100. Maltose as asubstrate (1.1%; 375 μl) was incubated for 5 minutes in a water bath at37° C. An aliquot of the enzyme sample was mixed with the substrate andspecific activity was measured at 37° C.

The Fusarium venenatum alpha-glucosidase has good thermostability(approximately 77% residual) up to about 65° C. as shown in FIG. 5. Theenzyme loses only 23% activity after 5 minutes in 50 mM acetate bufferpH 5.0 at this temperature and loses all activity at 100° C.

Kinetic parameters. The kinetic parameters for the specific hydrolysisof maltose by the purified Fusarium venenatum alpha-glucosidase weredetermined.

A Dionex BioLC HPLC device equipped with CarboPac PA10 4×250 mm columnand ED50 Electrochemical detector (Sunnyvale, Calif.) was used to detectglucose quantitatively from the hydrolysis of maltose. Sodium hydroxidesolution (200 mM) was applied as a liquid phase. This method providesprecise determination at the level of around 0.01 mM glucose. Thecalibration curve was linear between 0 mM and 1.2 mM glucose.

The incubation mixture contained 10 ml of maltose solution in the rangeof 0.17-5.7 mM at 37° C. The enzymatic reaction was initiated by adding10 μl of alpha-glucosidase solution. The enzymatic reaction wasterminated by placing 1 ml aliquot into boiling water for 2.5 minutesand then into ice for at least 30 minutes.

Values of k_(cat) were calculated using a molecular mass of 105.8 kDa.

The reciprocal plots, commonly used for determining kinetic parameters,were not linear for the enzyme. At elevated maltose concentrations, thevelocity of the hydrolysis reaction (accumulation of glucose) wassignificantly decreased.

The observed decreased velocity in alpha-glucosidase-catalyzedhydrolysis of maltose may be caused by substrate inhibition (Segel, I.H. Enzyme Kinetics. Behavior and Analysis of Rapid Equilibrium andSteady-State Enzyme Systems. 1975, John Wiley & Sons), or mayalternatively be the result of a competitive utilization of glucose in atransglycosylation reaction. As concentrations of maltose are increased,it becomes an acceptor for the glucose molecule. The transglycosylationreaction between the glucose and maltose leads to panose(6-O-alpha-D-glucosylmaltose). The probability of interaction betweentwo glucose molecules, which results in maltose and isomaltose, was lowdue to the low concentration of maltose at the “initial rate” regime.The CarboPac PA10 column allows separation of glucose fromoligosaccharides, but does not separate maltose and panose.

Kinetic parameters for the Fusarium venenatum alpha-glucosidase wereestimated from the plots. At pH 5.0 and 37° C., the K_(m) for theFusarium venenatum alpha-glucosidase was 0.13 mM and k_(cat) was 17 s⁻¹(substrate interval 0.17 mM-1.0 mM).

As indicated above, the substrate intervals were not always optimal. Atthe same time the detection limit did not allow the application of lowersubstrate concentrations. The Fusarium venenatum alpha-glucosidasedemonstrated strong “substrate inhibition” that can likely be attributedto the transglycosylation activity.

Deposit of Biological Material

The following biological material has been deposited under the terms ofthe Budapest Treaty with the Agricultural Research Service PatentCulture Collection, Northern Regional Research Center, 1815 UniversityStreet, Peoria, Ill., 61604, and given the following accession number:

Deposit Accession Number Date of Deposit E. coli pFD11F2 NRRL B-30753Jul. 1, 2004

The strain has been deposited under conditions that assure that accessto the cultures will be available during the pendency of this patentapplication to one determined by the Commissioner of Patents andTrademarks to be entitled thereto under 37 C.F.R. §1.14 and 35 U.S.C.§122. The deposit represents a substantially pure culture of thedeposited strains. The deposit is available as required by foreignpatent laws in countries wherein counterparts of the subjectapplication, or its progeny are filed. However, it should be understoodthat the availability of a deposit does not constitute a license topractice the subject invention in derogation of patent rights granted bygovernmental action.

The invention described and claimed herein is not to be limited in scopeby the specific aspects herein disclosed, since these aspects areintended as illustrations of several aspects of the invention. Anyequivalent aspects are intended to be within the scope of thisinvention. Indeed, various modifications of the invention in addition tothose shown and described herein will become apparent to those skilledin the art from the foregoing description. Such modifications are alsointended to fall within the scope of the appended claims. In the case ofconflict, the present disclosure including definitions will control.

Various references are cited herein, the disclosures of which areincorporated by reference in their entireties.

1. An isolated polynucleotide comprising a nucleotide sequence whichencodes a polypeptide having alpha-glucosidase activity, wherein theisolated polynucleotide is selected from the group consisting of: (a) apolynucleotide encoding a polypeptide having alpha-glucosidase activitycomprising an amino acid sequence which has at least 95% sequenceidentity to the mature polypeptide of SEQ ID NO: 2; (b) a polynucleotideencoding a polypeptide having alpha-glucosidase activity comprising anucleotide sequence which has at least 95% sequence identity to themature polypeptide coding sequence of SEQ ID NO: 1; and (c) apolynucleotide encoding a polypeptide having alpha-glucosidase activitycomprising a nucleotide sequence which hybridizes under at least highstringency conditions with (i) the mature polypeptide coding sequence ofSEQ ID NO: 1, (ii) the genomic DNA sequence comprising the maturepolypeptide coding sequence of SEQ ID NO: 1, or (iii) a full-lengthcomplementary strand of (i) or (ii).
 2. The polynucleotide of claim 1,wherein the polypeptide having alpha-glucosidase activity comprises anamino acid sequence which has at least 95% sequence identity to themature polypeptide of SEQ ID NO:
 2. 3. The polynucleotide of claim 2,wherein the polypeptide having alpha-glucosidase activity comprises anamino acid sequence which has at least 97% sequence identity to themature polypeptide of SEQ ID NO:
 2. 4. The polynucleotide of claim 1,wherein the polypeptide having alpha-glucosidase activity comprises orconsists of the amino acid sequence of SEQ ID NO: 2, or a fragmentthereof having alpha-glucosidase activity.
 5. The polynucleotide ofclaim 1, which comprises a nucleotide sequence which has at least 95%sequence identity to the mature polypeptide coding sequence of SEQ IDNO:
 1. 6. The polynucleotide of claim 5, which comprises a nucleotidesequence which has at least 97% sequence identity to the maturepolypeptide coding sequence of SEQ ID NO:
 1. 7. The polynucleotide ofclaim 1, which comprises or consists of the nucleotide sequence of SEQID NO: 1, or a subsequence thereof encoding a polypeptide fragmenthaving alpha-glucosidase activity.
 8. The polynucleotide of claim 1,which comprises a nucleotide sequence which hybridizes under at leasthigh stringency conditions with (i) the mature polypeptide codingsequence of SEQ ID NO: 1, (ii) the genomic DNA sequence comprising themature polypeptide coding sequence of SEQ ID NO: 1, or (iii) afull-length complementary strand of (i) or (ii).
 9. The polynucleotideof claim 1, which is contained in plasmid pFD11F2 which is contained inE. coli NRRL B-30753.
 10. The isolated polynucleotide of claim 1,wherein the mature polypeptide is amino acids 21 to 960 of SEQ ID NO: 2.11. The isolated polynucleotide of claim 1, wherein the maturepolypeptide coding sequence is nucleotides 61 to 2880 of SEQ ID NO: 1.12. A nucleic acid construct comprising the polynucleotide of claim 1operably linked to one or more control sequences that direct theproduction of the polypeptide having alpha-glucosidase activity in anexpression host.
 13. A recombinant expression vector comprising thenucleic acid construct of claim
 12. 14. An isolated transformed hostcell comprising the nucleic acid construct of claim
 12. 15. A method forproducing a polypeptide having alpha-glucosidase activity, comprising(a) cultivating a host cell comprising the nucleic acid construct ofclaim 12 under conditions conducive for production of the polypeptide;and (b) recovering the polypeptide.